Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1629 insertions, 0 deletions

diff --git a/third_party/rust/encoding_rs/src/utf_8.rs b/third_party/rust/encoding_rs/src/utf_8.rs
new file mode 100644
index 0000000000..da9cfc2880
--- /dev/null
+++ b/third_party/rust/encoding_rs/src/utf_8.rs
@@ -0,0 +1,1629 @@
+// Copyright Mozilla Foundation. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use super::*;
+use crate::ascii::ascii_to_basic_latin;
+use crate::ascii::basic_latin_to_ascii;
+use crate::ascii::validate_ascii;
+use crate::handles::*;
+use crate::mem::convert_utf16_to_utf8_partial;
+use crate::variant::*;
+
+cfg_if! {
+    if #[cfg(feature = "simd-accel")] {
+        use ::core::intrinsics::unlikely;
+        use ::core::intrinsics::likely;
+    } else {
+        #[inline(always)]
+        fn unlikely(b: bool) -> bool {
+            b
+        }
+        #[inline(always)]
+        fn likely(b: bool) -> bool {
+            b
+        }
+    }
+}
+
+#[repr(align(64))] // Align to cache lines
+pub struct Utf8Data {
+    pub table: [u8; 384],
+}
+
+// BEGIN GENERATED CODE. PLEASE DO NOT EDIT.
+// Instead, please regenerate using generate-encoding-data.py
+
+pub static UTF8_DATA: Utf8Data = Utf8Data {
+    table: [
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 148, 148, 148,
+        148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 164, 164, 164, 164, 164,
+        164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164,
+        164, 164, 164, 164, 164, 164, 164, 164, 164, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
+        252, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+        4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+        4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+        8, 8, 8, 8, 8, 8, 8, 16, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 32, 8, 8, 64, 8, 8, 8, 128, 4,
+        4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    ],
+};
+
+// END GENERATED CODE
+
+pub fn utf8_valid_up_to(src: &[u8]) -> usize {
+    let mut read = 0;
+    'outer: loop {
+        let mut byte = {
+            let src_remaining = &src[read..];
+            match validate_ascii(src_remaining) {
+                None => {
+                    return src.len();
+                }
+                Some((non_ascii, consumed)) => {
+                    read += consumed;
+                    non_ascii
+                }
+            }
+        };
+        // Check for the longest sequence to avoid checking twice for the
+        // multi-byte sequences. This can't overflow with 64-bit address space,
+        // because full 64 bits aren't in use. In the 32-bit PAE case, for this
+        // to overflow would mean that the source slice would be so large that
+        // the address space of the process would not have space for any code.
+        // Therefore, the slice cannot be so long that this would overflow.
+        if likely(read + 4 <= src.len()) {
+            'inner: loop {
+                // At this point, `byte` is not included in `read`, because we
+                // don't yet know that a) the UTF-8 sequence is valid and b) that there
+                // is output space if it is an astral sequence.
+                // Inspecting the lead byte directly is faster than what the
+                // std lib does!
+                if likely(in_inclusive_range8(byte, 0xC2, 0xDF)) {
+                    // Two-byte
+                    let second = unsafe { *(src.get_unchecked(read + 1)) };
+                    if !in_inclusive_range8(second, 0x80, 0xBF) {
+                        break 'outer;
+                    }
+                    read += 2;
+
+                    // Next lead (manually inlined)
+                    if likely(read + 4 <= src.len()) {
+                        byte = unsafe { *(src.get_unchecked(read)) };
+                        if byte < 0x80 {
+                            read += 1;
+                            continue 'outer;
+                        }
+                        continue 'inner;
+                    }
+                    break 'inner;
+                }
+                if likely(byte < 0xF0) {
+                    'three: loop {
+                        // Three-byte
+                        let second = unsafe { *(src.get_unchecked(read + 1)) };
+                        let third = unsafe { *(src.get_unchecked(read + 2)) };
+                        if ((UTF8_DATA.table[usize::from(second)]
+                            & unsafe { *(UTF8_DATA.table.get_unchecked(byte as usize + 0x80)) })
+                            | (third >> 6))
+                            != 2
+                        {
+                            break 'outer;
+                        }
+                        read += 3;
+
+                        // Next lead (manually inlined)
+                        if likely(read + 4 <= src.len()) {
+                            byte = unsafe { *(src.get_unchecked(read)) };
+                            if in_inclusive_range8(byte, 0xE0, 0xEF) {
+                                continue 'three;
+                            }
+                            if likely(byte < 0x80) {
+                                read += 1;
+                                continue 'outer;
+                            }
+                            continue 'inner;
+                        }
+                        break 'inner;
+                    }
+                }
+                // Four-byte
+                let second = unsafe { *(src.get_unchecked(read + 1)) };
+                let third = unsafe { *(src.get_unchecked(read + 2)) };
+                let fourth = unsafe { *(src.get_unchecked(read + 3)) };
+                if (u16::from(
+                    UTF8_DATA.table[usize::from(second)]
+                        & unsafe { *(UTF8_DATA.table.get_unchecked(byte as usize + 0x80)) },
+                ) | u16::from(third >> 6)
+                    | (u16::from(fourth & 0xC0) << 2))
+                    != 0x202
+                {
+                    break 'outer;
+                }
+                read += 4;
+
+                // Next lead
+                if likely(read + 4 <= src.len()) {
+                    byte = unsafe { *(src.get_unchecked(read)) };
+                    if byte < 0x80 {
+                        read += 1;
+                        continue 'outer;
+                    }
+                    continue 'inner;
+                }
+                break 'inner;
+            }
+        }
+        // We can't have a complete 4-byte sequence, but we could still have
+        // one to three shorter sequences.
+        'tail: loop {
+            // >= is better for bound check elision than ==
+            if read >= src.len() {
+                break 'outer;
+            }
+            byte = src[read];
+            // At this point, `byte` is not included in `read`, because we
+            // don't yet know that a) the UTF-8 sequence is valid and b) that there
+            // is output space if it is an astral sequence.
+            // Inspecting the lead byte directly is faster than what the
+            // std lib does!
+            if byte < 0x80 {
+                read += 1;
+                continue 'tail;
+            }
+            if in_inclusive_range8(byte, 0xC2, 0xDF) {
+                // Two-byte
+                let new_read = read + 2;
+                if new_read > src.len() {
+                    break 'outer;
+                }
+                let second = src[read + 1];
+                if !in_inclusive_range8(second, 0x80, 0xBF) {
+                    break 'outer;
+                }
+                read += 2;
+                continue 'tail;
+            }
+            // We need to exclude valid four byte lead bytes, because
+            // `UTF8_DATA.second_mask` covers
+            if byte < 0xF0 {
+                // Three-byte
+                let new_read = read + 3;
+                if new_read > src.len() {
+                    break 'outer;
+                }
+                let second = src[read + 1];
+                let third = src[read + 2];
+                if ((UTF8_DATA.table[usize::from(second)]
+                    & unsafe { *(UTF8_DATA.table.get_unchecked(byte as usize + 0x80)) })
+                    | (third >> 6))
+                    != 2
+                {
+                    break 'outer;
+                }
+                read += 3;
+                // `'tail` handles sequences shorter than 4, so
+                // there can't be another sequence after this one.
+                break 'outer;
+            }
+            break 'outer;
+        }
+    }
+    read
+}
+
+#[cfg_attr(feature = "cargo-clippy", allow(never_loop, cyclomatic_complexity))]
+pub fn convert_utf8_to_utf16_up_to_invalid(src: &[u8], dst: &mut [u16]) -> (usize, usize) {
+    let mut read = 0;
+    let mut written = 0;
+    'outer: loop {
+        let mut byte = {
+            let src_remaining = &src[read..];
+            let dst_remaining = &mut dst[written..];
+            let length = ::core::cmp::min(src_remaining.len(), dst_remaining.len());
+            match unsafe {
+                ascii_to_basic_latin(src_remaining.as_ptr(), dst_remaining.as_mut_ptr(), length)
+            } {
+                None => {
+                    read += length;
+                    written += length;
+                    break 'outer;
+                }
+                Some((non_ascii, consumed)) => {
+                    read += consumed;
+                    written += consumed;
+                    non_ascii
+                }
+            }
+        };
+        // Check for the longest sequence to avoid checking twice for the
+        // multi-byte sequences. This can't overflow with 64-bit address space,
+        // because full 64 bits aren't in use. In the 32-bit PAE case, for this
+        // to overflow would mean that the source slice would be so large that
+        // the address space of the process would not have space for any code.
+        // Therefore, the slice cannot be so long that this would overflow.
+        if likely(read + 4 <= src.len()) {
+            'inner: loop {
+                // At this point, `byte` is not included in `read`, because we
+                // don't yet know that a) the UTF-8 sequence is valid and b) that there
+                // is output space if it is an astral sequence.
+                // We know, thanks to `ascii_to_basic_latin` that there is output
+                // space for at least one UTF-16 code unit, so no need to check
+                // for output space in the BMP cases.
+                // Inspecting the lead byte directly is faster than what the
+                // std lib does!
+                if likely(in_inclusive_range8(byte, 0xC2, 0xDF)) {
+                    // Two-byte
+                    let second = unsafe { *(src.get_unchecked(read + 1)) };
+                    if !in_inclusive_range8(second, 0x80, 0xBF) {
+                        break 'outer;
+                    }
+                    unsafe {
+                        *(dst.get_unchecked_mut(written)) =
+                            ((u16::from(byte) & 0x1F) << 6) | (u16::from(second) & 0x3F)
+                    };
+                    read += 2;
+                    written += 1;
+
+                    // Next lead (manually inlined)
+                    if written == dst.len() {
+                        break 'outer;
+                    }
+                    if likely(read + 4 <= src.len()) {
+                        byte = unsafe { *(src.get_unchecked(read)) };
+                        if byte < 0x80 {
+                            unsafe { *(dst.get_unchecked_mut(written)) = u16::from(byte) };
+                            read += 1;
+                            written += 1;
+                            continue 'outer;
+                        }
+                        continue 'inner;
+                    }
+                    break 'inner;
+                }
+                if likely(byte < 0xF0) {
+                    'three: loop {
+                        // Three-byte
+                        let second = unsafe { *(src.get_unchecked(read + 1)) };
+                        let third = unsafe { *(src.get_unchecked(read + 2)) };
+                        if ((UTF8_DATA.table[usize::from(second)]
+                            & unsafe { *(UTF8_DATA.table.get_unchecked(byte as usize + 0x80)) })
+                            | (third >> 6))
+                            != 2
+                        {
+                            break 'outer;
+                        }
+                        let point = ((u16::from(byte) & 0xF) << 12)
+                            | ((u16::from(second) & 0x3F) << 6)
+                            | (u16::from(third) & 0x3F);
+                        unsafe { *(dst.get_unchecked_mut(written)) = point };
+                        read += 3;
+                        written += 1;
+
+                        // Next lead (manually inlined)
+                        if written == dst.len() {
+                            break 'outer;
+                        }
+                        if likely(read + 4 <= src.len()) {
+                            byte = unsafe { *(src.get_unchecked(read)) };
+                            if in_inclusive_range8(byte, 0xE0, 0xEF) {
+                                continue 'three;
+                            }
+                            if likely(byte < 0x80) {
+                                unsafe { *(dst.get_unchecked_mut(written)) = u16::from(byte) };
+                                read += 1;
+                                written += 1;
+                                continue 'outer;
+                            }
+                            continue 'inner;
+                        }
+                        break 'inner;
+                    }
+                }
+                // Four-byte
+                if written + 1 == dst.len() {
+                    break 'outer;
+                }
+                let second = unsafe { *(src.get_unchecked(read + 1)) };
+                let third = unsafe { *(src.get_unchecked(read + 2)) };
+                let fourth = unsafe { *(src.get_unchecked(read + 3)) };
+                if (u16::from(
+                    UTF8_DATA.table[usize::from(second)]
+                        & unsafe { *(UTF8_DATA.table.get_unchecked(byte as usize + 0x80)) },
+                ) | u16::from(third >> 6)
+                    | (u16::from(fourth & 0xC0) << 2))
+                    != 0x202
+                {
+                    break 'outer;
+                }
+                let point = ((u32::from(byte) & 0x7) << 18)
+                    | ((u32::from(second) & 0x3F) << 12)
+                    | ((u32::from(third) & 0x3F) << 6)
+                    | (u32::from(fourth) & 0x3F);
+                unsafe { *(dst.get_unchecked_mut(written)) = (0xD7C0 + (point >> 10)) as u16 };
+                unsafe {
+                    *(dst.get_unchecked_mut(written + 1)) = (0xDC00 + (point & 0x3FF)) as u16
+                };
+                read += 4;
+                written += 2;
+
+                // Next lead
+                if written == dst.len() {
+                    break 'outer;
+                }
+                if likely(read + 4 <= src.len()) {
+                    byte = unsafe { *(src.get_unchecked(read)) };
+                    if byte < 0x80 {
+                        unsafe { *(dst.get_unchecked_mut(written)) = u16::from(byte) };
+                        read += 1;
+                        written += 1;
+                        continue 'outer;
+                    }
+                    continue 'inner;
+                }
+                break 'inner;
+            }
+        }
+        // We can't have a complete 4-byte sequence, but we could still have
+        // one to three shorter sequences.
+        'tail: loop {
+            // >= is better for bound check elision than ==
+            if read >= src.len() || written >= dst.len() {
+                break 'outer;
+            }
+            byte = src[read];
+            // At this point, `byte` is not included in `read`, because we
+            // don't yet know that a) the UTF-8 sequence is valid and b) that there
+            // is output space if it is an astral sequence.
+            // Inspecting the lead byte directly is faster than what the
+            // std lib does!
+            if byte < 0x80 {
+                dst[written] = u16::from(byte);
+                read += 1;
+                written += 1;
+                continue 'tail;
+            }
+            if in_inclusive_range8(byte, 0xC2, 0xDF) {
+                // Two-byte
+                let new_read = read + 2;
+                if new_read > src.len() {
+                    break 'outer;
+                }
+                let second = src[read + 1];
+                if !in_inclusive_range8(second, 0x80, 0xBF) {
+                    break 'outer;
+                }
+                dst[written] = ((u16::from(byte) & 0x1F) << 6) | (u16::from(second) & 0x3F);
+                read += 2;
+                written += 1;
+                continue 'tail;
+            }
+            // We need to exclude valid four byte lead bytes, because
+            // `UTF8_DATA.second_mask` covers
+            if byte < 0xF0 {
+                // Three-byte
+                let new_read = read + 3;
+                if new_read > src.len() {
+                    break 'outer;
+                }
+                let second = src[read + 1];
+                let third = src[read + 2];
+                if ((UTF8_DATA.table[usize::from(second)]
+                    & unsafe { *(UTF8_DATA.table.get_unchecked(byte as usize + 0x80)) })
+                    | (third >> 6))
+                    != 2
+                {
+                    break 'outer;
+                }
+                let point = ((u16::from(byte) & 0xF) << 12)
+                    | ((u16::from(second) & 0x3F) << 6)
+                    | (u16::from(third) & 0x3F);
+                dst[written] = point;
+                read += 3;
+                written += 1;
+                // `'tail` handles sequences shorter than 4, so
+                // there can't be another sequence after this one.
+                break 'outer;
+            }
+            break 'outer;
+        }
+    }
+    (read, written)
+}
+
+pub struct Utf8Decoder {
+    code_point: u32,
+    bytes_seen: usize,   // 1, 2 or 3: counts continuations only
+    bytes_needed: usize, // 1, 2 or 3: counts continuations only
+    lower_boundary: u8,
+    upper_boundary: u8,
+}
+
+impl Utf8Decoder {
+    pub fn new_inner() -> Utf8Decoder {
+        Utf8Decoder {
+            code_point: 0,
+            bytes_seen: 0,
+            bytes_needed: 0,
+            lower_boundary: 0x80u8,
+            upper_boundary: 0xBFu8,
+        }
+    }
+
+    pub fn new() -> VariantDecoder {
+        VariantDecoder::Utf8(Utf8Decoder::new_inner())
+    }
+
+    pub fn in_neutral_state(&self) -> bool {
+        self.bytes_needed == 0
+    }
+
+    fn extra_from_state(&self) -> usize {
+        if self.bytes_needed == 0 {
+            0
+        } else {
+            self.bytes_seen + 1
+        }
+    }
+
+    pub fn max_utf16_buffer_length(&self, byte_length: usize) -> Option<usize> {
+        byte_length.checked_add(1 + self.extra_from_state())
+    }
+
+    pub fn max_utf8_buffer_length_without_replacement(&self, byte_length: usize) -> Option<usize> {
+        byte_length.checked_add(3 + self.extra_from_state())
+    }
+
+    pub fn max_utf8_buffer_length(&self, byte_length: usize) -> Option<usize> {
+        checked_add(
+            3,
+            checked_mul(3, byte_length.checked_add(self.extra_from_state())),
+        )
+    }
+
+    decoder_functions!(
+        {},
+        {
+            // This is the fast path. The rest runs only at the
+            // start and end for partial sequences.
+            if self.bytes_needed == 0 {
+                dest.copy_utf8_up_to_invalid_from(&mut source);
+            }
+        },
+        {
+            if self.bytes_needed != 0 {
+                let bad_bytes = (self.bytes_seen + 1) as u8;
+                self.code_point = 0;
+                self.bytes_needed = 0;
+                self.bytes_seen = 0;
+                return (
+                    DecoderResult::Malformed(bad_bytes, 0),
+                    src_consumed,
+                    dest.written(),
+                );
+            }
+        },
+        {
+            if self.bytes_needed == 0 {
+                if b < 0x80u8 {
+                    destination_handle.write_ascii(b);
+                    continue;
+                }
+                if b < 0xC2u8 {
+                    return (
+                        DecoderResult::Malformed(1, 0),
+                        unread_handle.consumed(),
+                        destination_handle.written(),
+                    );
+                }
+                if b < 0xE0u8 {
+                    self.bytes_needed = 1;
+                    self.code_point = u32::from(b) & 0x1F;
+                    continue;
+                }
+                if b < 0xF0u8 {
+                    if b == 0xE0u8 {
+                        self.lower_boundary = 0xA0u8;
+                    } else if b == 0xEDu8 {
+                        self.upper_boundary = 0x9Fu8;
+                    }
+                    self.bytes_needed = 2;
+                    self.code_point = u32::from(b) & 0xF;
+                    continue;
+                }
+                if b < 0xF5u8 {
+                    if b == 0xF0u8 {
+                        self.lower_boundary = 0x90u8;
+                    } else if b == 0xF4u8 {
+                        self.upper_boundary = 0x8Fu8;
+                    }
+                    self.bytes_needed = 3;
+                    self.code_point = u32::from(b) & 0x7;
+                    continue;
+                }
+                return (
+                    DecoderResult::Malformed(1, 0),
+                    unread_handle.consumed(),
+                    destination_handle.written(),
+                );
+            }
+            // self.bytes_needed != 0
+            if !(b >= self.lower_boundary && b <= self.upper_boundary) {
+                let bad_bytes = (self.bytes_seen + 1) as u8;
+                self.code_point = 0;
+                self.bytes_needed = 0;
+                self.bytes_seen = 0;
+                self.lower_boundary = 0x80u8;
+                self.upper_boundary = 0xBFu8;
+                return (
+                    DecoderResult::Malformed(bad_bytes, 0),
+                    unread_handle.unread(),
+                    destination_handle.written(),
+                );
+            }
+            self.lower_boundary = 0x80u8;
+            self.upper_boundary = 0xBFu8;
+            self.code_point = (self.code_point << 6) | (u32::from(b) & 0x3F);
+            self.bytes_seen += 1;
+            if self.bytes_seen != self.bytes_needed {
+                continue;
+            }
+            if self.bytes_needed == 3 {
+                destination_handle.write_astral(self.code_point);
+            } else {
+                destination_handle.write_bmp_excl_ascii(self.code_point as u16);
+            }
+            self.code_point = 0;
+            self.bytes_needed = 0;
+            self.bytes_seen = 0;
+            continue;
+        },
+        self,
+        src_consumed,
+        dest,
+        source,
+        b,
+        destination_handle,
+        unread_handle,
+        check_space_astral
+    );
+}
+
+#[cfg_attr(feature = "cargo-clippy", allow(never_loop))]
+#[inline(never)]
+pub fn convert_utf16_to_utf8_partial_inner(src: &[u16], dst: &mut [u8]) -> (usize, usize) {
+    let mut read = 0;
+    let mut written = 0;
+    'outer: loop {
+        let mut unit = {
+            let src_remaining = &src[read..];
+            let dst_remaining = &mut dst[written..];
+            let length = if dst_remaining.len() < src_remaining.len() {
+                dst_remaining.len()
+            } else {
+                src_remaining.len()
+            };
+            match unsafe {
+                basic_latin_to_ascii(src_remaining.as_ptr(), dst_remaining.as_mut_ptr(), length)
+            } {
+                None => {
+                    read += length;
+                    written += length;
+                    return (read, written);
+                }
+                Some((non_ascii, consumed)) => {
+                    read += consumed;
+                    written += consumed;
+                    non_ascii
+                }
+            }
+        };
+        'inner: loop {
+            // The following loop is only broken out of as a goto forward.
+            loop {
+                // Unfortunately, this check isn't enough for the compiler to elide
+                // the bound checks on writes to dst, which is why they are manually
+                // elided, which makes a measurable difference.
+                if written.checked_add(4).unwrap() > dst.len() {
+                    return (read, written);
+                }
+                read += 1;
+                if unit < 0x800 {
+                    unsafe {
+                        *(dst.get_unchecked_mut(written)) = (unit >> 6) as u8 | 0xC0u8;
+                        written += 1;
+                        *(dst.get_unchecked_mut(written)) = (unit & 0x3F) as u8 | 0x80u8;
+                        written += 1;
+                    }
+                    break;
+                }
+                let unit_minus_surrogate_start = unit.wrapping_sub(0xD800);
+                if likely(unit_minus_surrogate_start > (0xDFFF - 0xD800)) {
+                    unsafe {
+                        *(dst.get_unchecked_mut(written)) = (unit >> 12) as u8 | 0xE0u8;
+                        written += 1;
+                        *(dst.get_unchecked_mut(written)) = ((unit & 0xFC0) >> 6) as u8 | 0x80u8;
+                        written += 1;
+                        *(dst.get_unchecked_mut(written)) = (unit & 0x3F) as u8 | 0x80u8;
+                        written += 1;
+                    }
+                    break;
+                }
+                if likely(unit_minus_surrogate_start <= (0xDBFF - 0xD800)) {
+                    // high surrogate
+                    // read > src.len() is impossible, but using
+                    // >= instead of == allows the compiler to elide a bound check.
+                    if read >= src.len() {
+                        debug_assert_eq!(read, src.len());
+                        // Unpaired surrogate at the end of the buffer.
+                        unsafe {
+                            *(dst.get_unchecked_mut(written)) = 0xEFu8;
+                            written += 1;
+                            *(dst.get_unchecked_mut(written)) = 0xBFu8;
+                            written += 1;
+                            *(dst.get_unchecked_mut(written)) = 0xBDu8;
+                            written += 1;
+                        }
+                        return (read, written);
+                    }
+                    let second = src[read];
+                    let second_minus_low_surrogate_start = second.wrapping_sub(0xDC00);
+                    if likely(second_minus_low_surrogate_start <= (0xDFFF - 0xDC00)) {
+                        // The next code unit is a low surrogate. Advance position.
+                        read += 1;
+                        let astral = (u32::from(unit) << 10) + u32::from(second)
+                            - (((0xD800u32 << 10) - 0x10000u32) + 0xDC00u32);
+                        unsafe {
+                            *(dst.get_unchecked_mut(written)) = (astral >> 18) as u8 | 0xF0u8;
+                            written += 1;
+                            *(dst.get_unchecked_mut(written)) =
+                                ((astral & 0x3F000u32) >> 12) as u8 | 0x80u8;
+                            written += 1;
+                            *(dst.get_unchecked_mut(written)) =
+                                ((astral & 0xFC0u32) >> 6) as u8 | 0x80u8;
+                            written += 1;
+                            *(dst.get_unchecked_mut(written)) = (astral & 0x3F) as u8 | 0x80u8;
+                            written += 1;
+                        }
+                        break;
+                    }
+                    // The next code unit is not a low surrogate. Don't advance
+                    // position and treat the high surrogate as unpaired.
+                    // Fall through
+                }
+                // Unpaired low surrogate
+                unsafe {
+                    *(dst.get_unchecked_mut(written)) = 0xEFu8;
+                    written += 1;
+                    *(dst.get_unchecked_mut(written)) = 0xBFu8;
+                    written += 1;
+                    *(dst.get_unchecked_mut(written)) = 0xBDu8;
+                    written += 1;
+                }
+                break;
+            }
+            // Now see if the next unit is Basic Latin
+            // read > src.len() is impossible, but using
+            // >= instead of == allows the compiler to elide a bound check.
+            if read >= src.len() {
+                debug_assert_eq!(read, src.len());
+                return (read, written);
+            }
+            unit = src[read];
+            if unlikely(unit < 0x80) {
+                // written > dst.len() is impossible, but using
+                // >= instead of == allows the compiler to elide a bound check.
+                if written >= dst.len() {
+                    debug_assert_eq!(written, dst.len());
+                    return (read, written);
+                }
+                dst[written] = unit as u8;
+                read += 1;
+                written += 1;
+                // Mysteriously, adding a punctuation check here makes
+                // the expected benificiary cases *slower*!
+                continue 'outer;
+            }
+            continue 'inner;
+        }
+    }
+}
+
+#[inline(never)]
+pub fn convert_utf16_to_utf8_partial_tail(src: &[u16], dst: &mut [u8]) -> (usize, usize) {
+    // Everything below is cold code!
+    let mut read = 0;
+    let mut written = 0;
+    let mut unit = src[read];
+    // We now have up to 3 output slots, so an astral character
+    // will not fit.
+    if unit < 0x800 {
+        loop {
+            if unit < 0x80 {
+                if written >= dst.len() {
+                    return (read, written);
+                }
+                read += 1;
+                dst[written] = unit as u8;
+                written += 1;
+            } else if unit < 0x800 {
+                if written + 2 > dst.len() {
+                    return (read, written);
+                }
+                read += 1;
+                dst[written] = (unit >> 6) as u8 | 0xC0u8;
+                written += 1;
+                dst[written] = (unit & 0x3F) as u8 | 0x80u8;
+                written += 1;
+            } else {
+                return (read, written);
+            }
+            // read > src.len() is impossible, but using
+            // >= instead of == allows the compiler to elide a bound check.
+            if read >= src.len() {
+                debug_assert_eq!(read, src.len());
+                return (read, written);
+            }
+            unit = src[read];
+        }
+    }
+    // Could be an unpaired surrogate, but we'll need 3 output
+    // slots in any case.
+    if written + 3 > dst.len() {
+        return (read, written);
+    }
+    read += 1;
+    let unit_minus_surrogate_start = unit.wrapping_sub(0xD800);
+    if unit_minus_surrogate_start <= (0xDFFF - 0xD800) {
+        // Got surrogate
+        if unit_minus_surrogate_start <= (0xDBFF - 0xD800) {
+            // Got high surrogate
+            if read >= src.len() {
+                // Unpaired high surrogate
+                unit = 0xFFFD;
+            } else {
+                let second = src[read];
+                if in_inclusive_range16(second, 0xDC00, 0xDFFF) {
+                    // Valid surrogate pair, but we know it won't fit.
+                    read -= 1;
+                    return (read, written);
+                }
+                // Unpaired high
+                unit = 0xFFFD;
+            }
+        } else {
+            // Unpaired low
+            unit = 0xFFFD;
+        }
+    }
+    dst[written] = (unit >> 12) as u8 | 0xE0u8;
+    written += 1;
+    dst[written] = ((unit & 0xFC0) >> 6) as u8 | 0x80u8;
+    written += 1;
+    dst[written] = (unit & 0x3F) as u8 | 0x80u8;
+    written += 1;
+    debug_assert_eq!(written, dst.len());
+    (read, written)
+}
+
+pub struct Utf8Encoder;
+
+impl Utf8Encoder {
+    pub fn new(encoding: &'static Encoding) -> Encoder {
+        Encoder::new(encoding, VariantEncoder::Utf8(Utf8Encoder))
+    }
+
+    pub fn max_buffer_length_from_utf16_without_replacement(
+        &self,
+        u16_length: usize,
+    ) -> Option<usize> {
+        u16_length.checked_mul(3)
+    }
+
+    pub fn max_buffer_length_from_utf8_without_replacement(
+        &self,
+        byte_length: usize,
+    ) -> Option<usize> {
+        Some(byte_length)
+    }
+
+    pub fn encode_from_utf16_raw(
+        &mut self,
+        src: &[u16],
+        dst: &mut [u8],
+        _last: bool,
+    ) -> (EncoderResult, usize, usize) {
+        let (read, written) = convert_utf16_to_utf8_partial(src, dst);
+        (
+            if read == src.len() {
+                EncoderResult::InputEmpty
+            } else {
+                EncoderResult::OutputFull
+            },
+            read,
+            written,
+        )
+    }
+
+    pub fn encode_from_utf8_raw(
+        &mut self,
+        src: &str,
+        dst: &mut [u8],
+        _last: bool,
+    ) -> (EncoderResult, usize, usize) {
+        let bytes = src.as_bytes();
+        let mut to_write = bytes.len();
+        if to_write <= dst.len() {
+            (&mut dst[..to_write]).copy_from_slice(bytes);
+            return (EncoderResult::InputEmpty, to_write, to_write);
+        }
+        to_write = dst.len();
+        // Move back until we find a UTF-8 sequence boundary.
+        while (bytes[to_write] & 0xC0) == 0x80 {
+            to_write -= 1;
+        }
+        (&mut dst[..to_write]).copy_from_slice(&bytes[..to_write]);
+        (EncoderResult::OutputFull, to_write, to_write)
+    }
+}
+
+// Any copyright to the test code below this comment is dedicated to the
+// Public Domain. http://creativecommons.org/publicdomain/zero/1.0/
+
+#[cfg(all(test, feature = "alloc"))]
+mod tests {
+    use super::super::testing::*;
+    use super::super::*;
+
+    //    fn decode_utf8_to_utf16(bytes: &[u8], expect: &[u16]) {
+    //        decode_to_utf16_without_replacement(UTF_8, bytes, expect);
+    //    }
+
+    fn decode_utf8_to_utf8(bytes: &[u8], expect: &str) {
+        decode_to_utf8(UTF_8, bytes, expect);
+    }
+
+    fn decode_valid_utf8(string: &str) {
+        decode_utf8_to_utf8(string.as_bytes(), string);
+    }
+
+    fn encode_utf8_from_utf16(string: &[u16], expect: &[u8]) {
+        encode_from_utf16(UTF_8, string, expect);
+    }
+
+    fn encode_utf8_from_utf8(string: &str, expect: &[u8]) {
+        encode_from_utf8(UTF_8, string, expect);
+    }
+
+    fn encode_utf8_from_utf16_with_output_limit(
+        string: &[u16],
+        expect: &str,
+        limit: usize,
+        expect_result: EncoderResult,
+    ) {
+        let mut dst = Vec::new();
+        {
+            dst.resize(limit, 0u8);
+            let mut encoder = UTF_8.new_encoder();
+            let (result, read, written) =
+                encoder.encode_from_utf16_without_replacement(string, &mut dst, false);
+            assert_eq!(result, expect_result);
+            if expect_result == EncoderResult::InputEmpty {
+                assert_eq!(read, string.len());
+            }
+            assert_eq!(&dst[..written], expect.as_bytes());
+        }
+        {
+            dst.resize(64, 0u8);
+            for (i, elem) in dst.iter_mut().enumerate() {
+                *elem = i as u8;
+            }
+            let mut encoder = UTF_8.new_encoder();
+            let (_, _, mut j) =
+                encoder.encode_from_utf16_without_replacement(string, &mut dst, false);
+            while j < dst.len() {
+                assert_eq!(usize::from(dst[j]), j);
+                j += 1;
+            }
+        }
+    }
+
+    #[test]
+    fn test_utf8_decode() {
+        // Empty
+        decode_valid_utf8("");
+        // ASCII
+        decode_valid_utf8("ab");
+        // Low BMP
+        decode_valid_utf8("a\u{E4}Z");
+        // High BMP
+        decode_valid_utf8("a\u{2603}Z");
+        // Astral
+        decode_valid_utf8("a\u{1F4A9}Z");
+        // Low BMP with last byte missing
+        decode_utf8_to_utf8(b"a\xC3Z", "a\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xC3", "a\u{FFFD}");
+        // High BMP with last byte missing
+        decode_utf8_to_utf8(b"a\xE2\x98Z", "a\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xE2\x98", "a\u{FFFD}");
+        // Astral with last byte missing
+        decode_utf8_to_utf8(b"a\xF0\x9F\x92Z", "a\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xF0\x9F\x92", "a\u{FFFD}");
+        // Lone highest continuation
+        decode_utf8_to_utf8(b"a\xBFZ", "a\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xBF", "a\u{FFFD}");
+        // Two lone highest continuations
+        decode_utf8_to_utf8(b"a\xBF\xBFZ", "a\u{FFFD}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xBF\xBF", "a\u{FFFD}\u{FFFD}");
+        // Low BMP followed by lowest lone continuation
+        decode_utf8_to_utf8(b"a\xC3\xA4\x80Z", "a\u{E4}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xC3\xA4\x80", "a\u{E4}\u{FFFD}");
+        // Low BMP followed by highest lone continuation
+        decode_utf8_to_utf8(b"a\xC3\xA4\xBFZ", "a\u{E4}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xC3\xA4\xBF", "a\u{E4}\u{FFFD}");
+        // High BMP followed by lowest lone continuation
+        decode_utf8_to_utf8(b"a\xE2\x98\x83\x80Z", "a\u{2603}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xE2\x98\x83\x80", "a\u{2603}\u{FFFD}");
+        // High BMP followed by highest lone continuation
+        decode_utf8_to_utf8(b"a\xE2\x98\x83\xBFZ", "a\u{2603}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xE2\x98\x83\xBF", "a\u{2603}\u{FFFD}");
+        // Astral followed by lowest lone continuation
+        decode_utf8_to_utf8(b"a\xF0\x9F\x92\xA9\x80Z", "a\u{1F4A9}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xF0\x9F\x92\xA9\x80", "a\u{1F4A9}\u{FFFD}");
+        // Astral followed by highest lone continuation
+        decode_utf8_to_utf8(b"a\xF0\x9F\x92\xA9\xBFZ", "a\u{1F4A9}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\xF0\x9F\x92\xA9\xBF", "a\u{1F4A9}\u{FFFD}");
+
+        // Boundary conditions
+        // Lowest single-byte
+        decode_valid_utf8("Z\x00");
+        decode_valid_utf8("Z\x00Z");
+        // Lowest single-byte as two-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xC0\x80", "a\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xC0\x80Z", "a\u{FFFD}\u{FFFD}Z");
+        // Lowest single-byte as three-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xE0\x80\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xE0\x80\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Lowest single-byte as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x80\x80\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x80\x80\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // One below lowest single-byte
+        decode_utf8_to_utf8(b"a\xFF", "a\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xFFZ", "a\u{FFFD}Z");
+        // Highest single-byte
+        decode_valid_utf8("a\x7F");
+        decode_valid_utf8("a\x7FZ");
+        // Highest single-byte as two-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xC1\xBF", "a\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xC1\xBFZ", "a\u{FFFD}\u{FFFD}Z");
+        // Highest single-byte as three-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xE0\x81\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xE0\x81\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Highest single-byte as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x80\x81\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x80\x81\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // One past highest single byte (also lone continuation)
+        decode_utf8_to_utf8(b"a\x80Z", "a\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\x80", "a\u{FFFD}");
+        // Two lone continuations
+        decode_utf8_to_utf8(b"a\x80\x80Z", "a\u{FFFD}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\x80\x80", "a\u{FFFD}\u{FFFD}");
+        // Three lone continuations
+        decode_utf8_to_utf8(b"a\x80\x80\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\x80\x80\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}");
+        // Four lone continuations
+        decode_utf8_to_utf8(b"a\x80\x80\x80\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        decode_utf8_to_utf8(b"a\x80\x80\x80\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        // Lowest two-byte
+        decode_utf8_to_utf8(b"a\xC2\x80", "a\u{0080}");
+        decode_utf8_to_utf8(b"a\xC2\x80Z", "a\u{0080}Z");
+        // Lowest two-byte as three-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xE0\x82\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xE0\x82\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Lowest two-byte as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x80\x82\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x80\x82\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Lead one below lowest two-byte
+        decode_utf8_to_utf8(b"a\xC1\x80", "a\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xC1\x80Z", "a\u{FFFD}\u{FFFD}Z");
+        // Trail one below lowest two-byte
+        decode_utf8_to_utf8(b"a\xC2\x7F", "a\u{FFFD}\u{007F}");
+        decode_utf8_to_utf8(b"a\xC2\x7FZ", "a\u{FFFD}\u{007F}Z");
+        // Highest two-byte
+        decode_utf8_to_utf8(b"a\xDF\xBF", "a\u{07FF}");
+        decode_utf8_to_utf8(b"a\xDF\xBFZ", "a\u{07FF}Z");
+        // Highest two-byte as three-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xE0\x9F\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xE0\x9F\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Highest two-byte as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x80\x9F\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x80\x9F\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Lowest three-byte
+        decode_utf8_to_utf8(b"a\xE0\xA0\x80", "a\u{0800}");
+        decode_utf8_to_utf8(b"a\xE0\xA0\x80Z", "a\u{0800}Z");
+        // Lowest three-byte as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x80\xA0\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x80\xA0\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Highest below surrogates
+        decode_utf8_to_utf8(b"a\xED\x9F\xBF", "a\u{D7FF}");
+        decode_utf8_to_utf8(b"a\xED\x9F\xBFZ", "a\u{D7FF}Z");
+        // Highest below surrogates as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x8D\x9F\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x8D\x9F\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // First surrogate
+        decode_utf8_to_utf8(b"a\xED\xA0\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xED\xA0\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // First surrogate as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x8D\xA0\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x8D\xA0\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Last surrogate
+        decode_utf8_to_utf8(b"a\xED\xBF\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xED\xBF\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Last surrogate as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x8D\xBF\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x8D\xBF\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Lowest above surrogates
+        decode_utf8_to_utf8(b"a\xEE\x80\x80", "a\u{E000}");
+        decode_utf8_to_utf8(b"a\xEE\x80\x80Z", "a\u{E000}Z");
+        // Lowest above surrogates as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x8E\x80\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x8E\x80\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Highest three-byte
+        decode_utf8_to_utf8(b"a\xEF\xBF\xBF", "a\u{FFFF}");
+        decode_utf8_to_utf8(b"a\xEF\xBF\xBFZ", "a\u{FFFF}Z");
+        // Highest three-byte as four-byte overlong sequence
+        decode_utf8_to_utf8(b"a\xF0\x8F\xBF\xBF", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF0\x8F\xBF\xBFZ", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+        // Lowest four-byte
+        decode_utf8_to_utf8(b"a\xF0\x90\x80\x80", "a\u{10000}");
+        decode_utf8_to_utf8(b"a\xF0\x90\x80\x80Z", "a\u{10000}Z");
+        // Highest four-byte
+        decode_utf8_to_utf8(b"a\xF4\x8F\xBF\xBF", "a\u{10FFFF}");
+        decode_utf8_to_utf8(b"a\xF4\x8F\xBF\xBFZ", "a\u{10FFFF}Z");
+        // One past highest four-byte
+        decode_utf8_to_utf8(b"a\xF4\x90\x80\x80", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF4\x90\x80\x80Z", "a\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}Z");
+
+        // Highest four-byte with last byte replaced with 0xFF
+        decode_utf8_to_utf8(b"a\xF4\x8F\xBF\xFF", "a\u{FFFD}\u{FFFD}");
+        decode_utf8_to_utf8(b"a\xF4\x8F\xBF\xFFZ", "a\u{FFFD}\u{FFFD}Z");
+    }
+
+    #[test]
+    fn test_utf8_encode() {
+        // Empty
+        encode_utf8_from_utf16(&[], b"");
+        encode_utf8_from_utf8("", b"");
+
+        encode_utf8_from_utf16(&[0x0000], "\u{0000}".as_bytes());
+        encode_utf8_from_utf16(&[0x007F], "\u{007F}".as_bytes());
+        encode_utf8_from_utf16(&[0x0080], "\u{0080}".as_bytes());
+        encode_utf8_from_utf16(&[0x07FF], "\u{07FF}".as_bytes());
+        encode_utf8_from_utf16(&[0x0800], "\u{0800}".as_bytes());
+        encode_utf8_from_utf16(&[0xD7FF], "\u{D7FF}".as_bytes());
+        encode_utf8_from_utf16(&[0xD800], "\u{FFFD}".as_bytes());
+        encode_utf8_from_utf16(&[0xD800, 0x0062], "\u{FFFD}\u{0062}".as_bytes());
+        encode_utf8_from_utf16(&[0xDFFF], "\u{FFFD}".as_bytes());
+        encode_utf8_from_utf16(&[0xDFFF, 0x0062], "\u{FFFD}\u{0062}".as_bytes());
+        encode_utf8_from_utf16(&[0xE000], "\u{E000}".as_bytes());
+        encode_utf8_from_utf16(&[0xFFFF], "\u{FFFF}".as_bytes());
+        encode_utf8_from_utf16(&[0xD800, 0xDC00], "\u{10000}".as_bytes());
+        encode_utf8_from_utf16(&[0xDBFF, 0xDFFF], "\u{10FFFF}".as_bytes());
+        encode_utf8_from_utf16(&[0xDC00, 0xDEDE], "\u{FFFD}\u{FFFD}".as_bytes());
+    }
+
+    #[test]
+    fn test_encode_utf8_from_utf16_with_output_limit() {
+        encode_utf8_from_utf16_with_output_limit(&[0x0062], "\u{62}", 1, EncoderResult::InputEmpty);
+        encode_utf8_from_utf16_with_output_limit(&[0x00A7], "\u{A7}", 2, EncoderResult::InputEmpty);
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x2603],
+            "\u{2603}",
+            3,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDCA9],
+            "\u{1F4A9}",
+            4,
+            EncoderResult::InputEmpty,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(&[0x00A7], "", 1, EncoderResult::OutputFull);
+        encode_utf8_from_utf16_with_output_limit(&[0x2603], "", 2, EncoderResult::OutputFull);
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDCA9],
+            "",
+            3,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x0062],
+            "\u{63}\u{62}",
+            2,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00A7],
+            "\u{63}\u{A7}",
+            3,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x2603],
+            "\u{63}\u{2603}",
+            4,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0xD83D, 0xDCA9],
+            "\u{63}\u{1F4A9}",
+            5,
+            EncoderResult::InputEmpty,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00A7],
+            "\u{63}",
+            2,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x2603],
+            "\u{63}",
+            3,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0xD83D, 0xDCA9],
+            "\u{63}",
+            4,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x00B6, 0x0062],
+            "\u{B6}\u{62}",
+            3,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x00B6, 0x00A7],
+            "\u{B6}\u{A7}",
+            4,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x00B6, 0x2603],
+            "\u{B6}\u{2603}",
+            5,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x00B6, 0xD83D, 0xDCA9],
+            "\u{B6}\u{1F4A9}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x00B6, 0x00A7],
+            "\u{B6}",
+            3,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x00B6, 0x2603],
+            "\u{B6}",
+            4,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x00B6, 0xD83D, 0xDCA9],
+            "\u{B6}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x0062],
+            "\u{263A}\u{62}",
+            4,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x00A7],
+            "\u{263A}\u{A7}",
+            5,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x2603],
+            "\u{263A}\u{2603}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0xD83D, 0xDCA9],
+            "\u{263A}\u{1F4A9}",
+            7,
+            EncoderResult::InputEmpty,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x00A7],
+            "\u{263A}",
+            4,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x2603],
+            "\u{263A}",
+            5,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0xD83D, 0xDCA9],
+            "\u{263A}",
+            6,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDE0E, 0x0062],
+            "\u{1F60E}\u{62}",
+            5,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDE0E, 0x00A7],
+            "\u{1F60E}\u{A7}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDE0E, 0x2603],
+            "\u{1F60E}\u{2603}",
+            7,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDE0E, 0xD83D, 0xDCA9],
+            "\u{1F60E}\u{1F4A9}",
+            8,
+            EncoderResult::InputEmpty,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDE0E, 0x00A7],
+            "\u{1F60E}",
+            5,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDE0E, 0x2603],
+            "\u{1F60E}",
+            6,
+            EncoderResult::OutputFull,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0xD83D, 0xDE0E, 0xD83D, 0xDCA9],
+            "\u{1F60E}",
+            7,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x0062, 0x0062],
+            "\u{63}\u{B6}\u{62}\u{62}",
+            5,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x0062, 0x0062],
+            "\u{63}\u{B6}\u{62}",
+            4,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x0062, 0x0062, 0x0062],
+            "\u{63}\u{B6}\u{62}\u{62}\u{62}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x0062, 0x0062, 0x0062],
+            "\u{63}\u{B6}\u{62}\u{62}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x0062, 0x0062],
+            "\u{263A}\u{62}\u{62}",
+            5,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x0062, 0x0062],
+            "\u{263A}\u{62}",
+            4,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x0062, 0x0062, 0x0062],
+            "\u{263A}\u{62}\u{62}\u{62}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x0062, 0x0062, 0x0062],
+            "\u{263A}\u{62}\u{62}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x00A7],
+            "\u{63}\u{B6}\u{A7}",
+            5,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x00A7],
+            "\u{63}\u{B6}",
+            4,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x00A7, 0x0062],
+            "\u{63}\u{B6}\u{A7}\u{62}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x00A7, 0x0062],
+            "\u{63}\u{B6}\u{A7}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x00A7, 0x0062],
+            "\u{263A}\u{A7}\u{62}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x00A7, 0x0062],
+            "\u{263A}\u{A7}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x0062, 0x00A7],
+            "\u{63}\u{B6}\u{62}\u{A7}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x0062, 0x00A7],
+            "\u{63}\u{B6}\u{62}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x0062, 0x00A7],
+            "\u{263A}\u{62}\u{A7}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x0062, 0x00A7],
+            "\u{263A}\u{62}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x2603],
+            "\u{63}\u{B6}\u{2603}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0x2603],
+            "\u{63}\u{B6}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x2603],
+            "\u{263A}\u{2603}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0x2603],
+            "\u{263A}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0xD83D],
+            "\u{63}\u{B6}\u{FFFD}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0xD83D],
+            "\u{63}\u{B6}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0xD83D],
+            "\u{263A}\u{FFFD}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0xD83D],
+            "\u{263A}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0xDCA9],
+            "\u{63}\u{B6}\u{FFFD}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x0063, 0x00B6, 0xDCA9],
+            "\u{63}\u{B6}",
+            5,
+            EncoderResult::OutputFull,
+        );
+
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0xDCA9],
+            "\u{263A}\u{FFFD}",
+            6,
+            EncoderResult::InputEmpty,
+        );
+        encode_utf8_from_utf16_with_output_limit(
+            &[0x263A, 0xDCA9],
+            "\u{263A}",
+            5,
+            EncoderResult::OutputFull,
+        );
+    }
+
+    #[test]
+    fn test_utf8_max_length_from_utf16() {
+        let mut encoder = UTF_8.new_encoder();
+        let mut output = [0u8; 13];
+        let input = &[0x2C9Fu16, 0x2CA9u16, 0x2CA3u16, 0x2C9Fu16];
+        let needed = encoder
+            .max_buffer_length_from_utf16_without_replacement(input.len())
+            .unwrap();
+        let (result, _, _) =
+            encoder.encode_from_utf16_without_replacement(input, &mut output[..needed], true);
+        assert_eq!(result, EncoderResult::InputEmpty);
+    }
+
+    #[test]
+    fn test_decode_bom_prefixed_split_byte_triple() {
+        let mut output = [0u16; 20];
+        let mut decoder = UTF_8.new_decoder();
+        {
+            let needed = decoder.max_utf16_buffer_length(1).unwrap();
+            let (result, read, written, had_errors) =
+                decoder.decode_to_utf16(b"\xEF", &mut output[..needed], false);
+            assert_eq!(result, CoderResult::InputEmpty);
+            assert_eq!(read, 1);
+            assert_eq!(written, 0);
+            assert!(!had_errors);
+        }
+        {
+            let needed = decoder.max_utf16_buffer_length(1).unwrap();
+            let (result, read, written, had_errors) =
+                decoder.decode_to_utf16(b"\xBF", &mut output[..needed], false);
+            assert_eq!(result, CoderResult::InputEmpty);
+            assert_eq!(read, 1);
+            assert_eq!(written, 0);
+            assert!(!had_errors);
+        }
+        {
+            let needed = decoder.max_utf16_buffer_length(1).unwrap();
+            let (result, read, written, had_errors) =
+                decoder.decode_to_utf16(b"\xBE", &mut output[..needed], true);
+            assert_eq!(result, CoderResult::InputEmpty);
+            assert_eq!(read, 1);
+            assert_eq!(written, 1);
+            assert!(!had_errors);
+            assert_eq!(output[0], 0xFFFE);
+        }
+    }
+
+    #[test]
+    fn test_decode_bom_prefixed_split_byte_pair() {
+        let mut output = [0u16; 20];
+        let mut decoder = UTF_8.new_decoder();
+        {
+            let needed = decoder.max_utf16_buffer_length(1).unwrap();
+            let (result, read, written, had_errors) =
+                decoder.decode_to_utf16(b"\xEF", &mut output[..needed], false);
+            assert_eq!(result, CoderResult::InputEmpty);
+            assert_eq!(read, 1);
+            assert_eq!(written, 0);
+            assert!(!had_errors);
+        }
+        {
+            let needed = decoder.max_utf16_buffer_length(1).unwrap();
+            let (result, read, written, had_errors) =
+                decoder.decode_to_utf16(b"\xBC", &mut output[..needed], true);
+            assert_eq!(result, CoderResult::InputEmpty);
+            assert_eq!(read, 1);
+            assert_eq!(written, 1);
+            assert!(had_errors);
+            assert_eq!(output[0], 0xFFFD);
+        }
+    }
+
+    #[test]
+    fn test_decode_bom_prefix() {
+        let mut output = [0u16; 20];
+        let mut decoder = UTF_8.new_decoder();
+        {
+            let needed = decoder.max_utf16_buffer_length(1).unwrap();
+            let (result, read, written, had_errors) =
+                decoder.decode_to_utf16(b"\xEF", &mut output[..needed], true);
+            assert_eq!(result, CoderResult::InputEmpty);
+            assert_eq!(read, 1);
+            assert_eq!(written, 1);
+            assert!(had_errors);
+            assert_eq!(output[0], 0xFFFD);
+        }
+    }
+
+    #[test]
+    fn test_tail() {
+        let mut output = [0u16; 1];
+        let mut decoder = UTF_8.new_decoder_without_bom_handling();
+        {
+            let (result, read, written, had_errors) =
+                decoder.decode_to_utf16("\u{E4}a".as_bytes(), &mut output[..], false);
+            assert_eq!(result, CoderResult::OutputFull);
+            assert_eq!(read, 2);
+            assert_eq!(written, 1);
+            assert!(!had_errors);
+            assert_eq!(output[0], 0x00E4);
+        }
+    }
+}