1 files changed, 93 insertions, 0 deletions
diff --git a/vendor/ruzstd/src/decoding/dictionary.rs b/vendor/ruzstd/src/decoding/dictionary.rs
new file mode 100644
index 000000000..51fbcdf0b
--- /dev/null
+++ b/vendor/ruzstd/src/decoding/dictionary.rs
@@ -0,0 +1,93 @@
+use std::convert::TryInto;
+
+use crate::decoding::scratch::FSEScratch;
+use crate::decoding::scratch::HuffmanScratch;
+use crate::fse::FSETableError;
+use crate::huff0::HuffmanTableError;
+
+pub struct Dictionary {
+    pub id: u32,
+    pub fse: FSEScratch,
+    pub huf: HuffmanScratch,
+    pub dict_content: Vec<u8>,
+    pub offset_hist: [u32; 3],
+}
+
+#[derive(Debug, thiserror::Error)]
+#[non_exhaustive]
+pub enum DictionaryDecodeError {
+    #[error(
+        "Bad magic_num at start of the dictionary; Got: {got:#04X?}, Expected: {MAGIC_NUM:#04x?}"
+    )]
+    BadMagicNum { got: [u8; 4] },
+    #[error(transparent)]
+    FSETableError(#[from] FSETableError),
+    #[error(transparent)]
+    HuffmanTableError(#[from] HuffmanTableError),
+}
+
+pub const MAGIC_NUM: [u8; 4] = [0x37, 0xA4, 0x30, 0xEC];
+
+impl Dictionary {
+    /// parses the dictionary and set the tables
+    /// it returns the dict_id for checking with the frame's dict_id
+    pub fn decode_dict(raw: &[u8]) -> Result<Dictionary, DictionaryDecodeError> {
+        let mut new_dict = Dictionary {
+            id: 0,
+            fse: FSEScratch::new(),
+            huf: HuffmanScratch::new(),
+            dict_content: Vec::new(),
+            offset_hist: [2, 4, 8],
+        };
+
+        let magic_num: [u8; 4] = raw[..4].try_into().expect("optimized away");
+        if magic_num != MAGIC_NUM {
+            return Err(DictionaryDecodeError::BadMagicNum { got: magic_num });
+        }
+
+        let dict_id = raw[4..8].try_into().expect("optimized away");
+        let dict_id = u32::from_le_bytes(dict_id);
+        new_dict.id = dict_id;
+
+        let raw_tables = &raw[8..];
+
+        let huf_size = new_dict.huf.table.build_decoder(raw_tables)?;
+        let raw_tables = &raw_tables[huf_size as usize..];
+
+        let of_size = new_dict.fse.offsets.build_decoder(
+            raw_tables,
+            crate::decoding::sequence_section_decoder::OF_MAX_LOG,
+        )?;
+        let raw_tables = &raw_tables[of_size..];
+
+        let ml_size = new_dict.fse.match_lengths.build_decoder(
+            raw_tables,
+            crate::decoding::sequence_section_decoder::ML_MAX_LOG,
+        )?;
+        let raw_tables = &raw_tables[ml_size..];
+
+        let ll_size = new_dict.fse.literal_lengths.build_decoder(
+            raw_tables,
+            crate::decoding::sequence_section_decoder::LL_MAX_LOG,
+        )?;
+        let raw_tables = &raw_tables[ll_size..];
+
+        let offset1 = raw_tables[0..4].try_into().expect("optimized away");
+        let offset1 = u32::from_le_bytes(offset1);
+
+        let offset2 = raw_tables[4..8].try_into().expect("optimized away");
+        let offset2 = u32::from_le_bytes(offset2);
+
+        let offset3 = raw_tables[8..12].try_into().expect("optimized away");
+        let offset3 = u32::from_le_bytes(offset3);
+
+        new_dict.offset_hist[0] = offset1;
+        new_dict.offset_hist[1] = offset2;
+        new_dict.offset_hist[2] = offset3;
+
+        let raw_content = &raw_tables[12..];
+        new_dict.dict_content.extend(raw_content);
+
+        Ok(new_dict)
+    }
+}