1 files changed, 116 insertions, 0 deletions
diff --git a/third_party/rust/base64-0.10.1/examples/make_tables.rs b/third_party/rust/base64-0.10.1/examples/make_tables.rs
new file mode 100644
index 0000000000..9f170c047a
--- /dev/null
+++ b/third_party/rust/base64-0.10.1/examples/make_tables.rs
@@ -0,0 +1,116 @@
+use std::collections::HashMap;
+use std::iter::Iterator;
+
+fn main() {
+    println!("pub const INVALID_VALUE: u8 = 255;");
+
+    // A-Z
+    let standard_alphabet: Vec<u8> = (0x41..0x5B)
+        // a-z
+        .chain(0x61..0x7B)
+        // 0-9
+        .chain(0x30..0x3A)
+        // +
+        .chain(0x2B..0x2C)
+        // /
+        .chain(0x2F..0x30)
+        .collect();
+    print_encode_table(&standard_alphabet, "STANDARD_ENCODE", 0);
+    print_decode_table(&standard_alphabet, "STANDARD_DECODE", 0);
+
+    // A-Z
+    let url_alphabet: Vec<u8> = (0x41..0x5B)
+        // a-z
+        .chain(0x61..0x7B)
+        // 0-9
+        .chain(0x30..0x3A)
+        // -
+        .chain(0x2D..0x2E)
+        // _s
+        .chain(0x5F..0x60)
+        .collect();
+    print_encode_table(&url_alphabet, "URL_SAFE_ENCODE", 0);
+    print_decode_table(&url_alphabet, "URL_SAFE_DECODE", 0);
+
+    // ./0123456789
+    let crypt_alphabet: Vec<u8> = (b'.'..(b'9' + 1))
+        // A-Z
+        .chain(b'A'..(b'Z' + 1))
+        // a-z
+        .chain(b'a'..(b'z' + 1))
+        .collect();
+    print_encode_table(&crypt_alphabet, "CRYPT_ENCODE", 0);
+    print_decode_table(&crypt_alphabet, "CRYPT_DECODE", 0);
+}
+
+fn print_encode_table(alphabet: &[u8], const_name: &str, indent_depth: usize) {
+    println!("#[cfg_attr(rustfmt, rustfmt_skip)]");
+    println!(
+        "{:width$}pub const {}: &'static [u8; 64] = &[",
+        "",
+        const_name,
+        width = indent_depth
+    );
+
+    for (i, b) in alphabet.iter().enumerate() {
+        println!(
+            "{:width$}{}, // input {} (0x{:X}) => '{}' (0x{:X})",
+            "",
+            b,
+            i,
+            i,
+            String::from_utf8(vec![*b as u8]).unwrap(),
+            b,
+            width = indent_depth + 4
+        );
+    }
+
+    println!("{:width$}];", "", width = indent_depth);
+}
+
+fn print_decode_table(alphabet: &[u8], const_name: &str, indent_depth: usize) {
+    // map of alphabet bytes to 6-bit morsels
+    let mut input_to_morsel = HashMap::<u8, u8>::new();
+
+    // standard base64 alphabet bytes, in order
+    for (morsel, ascii_byte) in alphabet.iter().enumerate() {
+        // truncation cast is fine here
+        let _ = input_to_morsel.insert(*ascii_byte, morsel as u8);
+    }
+
+    println!("#[cfg_attr(rustfmt, rustfmt_skip)]");
+    println!(
+        "{:width$}pub const {}: &'static [u8; 256] = &[",
+        "",
+        const_name,
+        width = indent_depth
+    );
+    for ascii_byte in 0..256 {
+        let (value, comment) = match input_to_morsel.get(&(ascii_byte as u8)) {
+            None => (
+                "INVALID_VALUE".to_string(),
+                format!("input {} (0x{:X})", ascii_byte, ascii_byte),
+            ),
+            Some(v) => (
+                format!("{}", *v),
+                format!(
+                    "input {} (0x{:X} char '{}') => {} (0x{:X})",
+                    ascii_byte,
+                    ascii_byte,
+                    String::from_utf8(vec![ascii_byte as u8]).unwrap(),
+                    *v,
+                    *v
+                ),
+            ),
+        };
+
+        println!(
+            "{:width$}{}, // {}",
+            "",
+            value,
+            comment,
+            width = indent_depth + 4
+        );
+    }
+    println!("{:width$}];", "", width = indent_depth);
+}