feat: Implement proposal-arraybuffer-base64

Cargo.toml

@@ -147,6 +147,8 @@ strum = { version = "0.28", features = ["derive"] }
 unsend = { version = "0.2.1", default-features = false }
 husky-rs = "0.3.2"
 async-channel = "2.5.0"
+data-encoding = "2.11.0"
+data-encoding-macro = "0.1.20"
 
 # ICU4X core
 

core/engine/Cargo.toml

@@ -142,6 +142,8 @@ dynify = { workspace = true, features = ["macros"] }
 futures-concurrency.workspace = true
 oneshot = { workspace = true, features = ["async"] }
 async-channel.workspace = true
+data-encoding.workspace = true
+data-encoding-macro.workspace = true
 
 # intl deps
 boa_icu_provider = { workspace = true, features = ["std"], optional = true }

core/engine/src/builtins/typed_array/base64.rs

@@ -0,0 +1,256 @@
+//! Base64 helpers for `Uint8Array` proposal methods.
+//!
+//! This is adapted from the `ecma262` helper in the `data-encoding` repository so that
+//! `Uint8Array.{fromBase64,setFromBase64}` follow the proposal's partial-decoding rules.
+
+use data_encoding::{Character, DecodeError, DecodeKind, DecodePartial, Encoding};
+use data_encoding_macro::new_encoding;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) enum Alphabet {
+    Base64,
+    Base64Url,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) enum LastChunkHandling {
+    Loose,
+    Strict,
+    StopBeforePartial,
+}
+use LastChunkHandling::{Loose, StopBeforePartial, Strict};
+
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) struct DecodeMutResult {
+    pub(crate) read: usize,
+    pub(crate) written: usize,
+    pub(crate) error: Option<DecodeError>,
+}
+
+/// Decodes `input` in `output` according to the given parameters.
+///
+/// # Panics
+///
+/// Panics if `output.len() < 6 * input.len() / 8`. It is not an error if `max_length` is smaller
+/// than `output.len()`. This function will however not optimize those cases.
+pub(crate) fn decode_mut(
+    input: &[u8],
+    output: &mut [u8],
+    alphabet: Alphabet,
+    last_chunk_handling: LastChunkHandling,
+    max_length: Option<usize>,
+) -> DecodeMutResult {
+    // Select the appropriate encoding.
+    let base = match alphabet {
+        Alphabet::Base64 => &BASE64,
+        Alphabet::Base64Url => &BASE64URL,
+    };
+    let max_length = max_length.unwrap_or(usize::MAX);
+
+    // Decode as much as possible.
+    let (mut read, mut written) = match base.decode_mut(input, &mut output[..6 * input.len() / 8]) {
+        Ok(olen) => (input.len(), olen),
+        Err(DecodePartial { read, written, .. }) => (read, written),
+    };
+
+    // Backtrack to the last complete chunk that fits below the maximum output length.
+    let extra_output = written - core::cmp::min(written, max_length) / 3 * 3;
+    let mut extra_input = (8 * extra_output).div_ceil(6);
+    written -= extra_output;
+    loop {
+        // Backtrack white-spaces.
+        while 0 < read && base.interpret_byte(input[read - 1]).is_ignored() {
+            read -= 1;
+        }
+        if extra_input == 0 {
+            break;
+        }
+        // Backtrack one symbol.
+        read -= 1;
+        extra_input -= 1;
+        debug_assert!(base.interpret_byte(input[read]).is_symbol().is_some());
+    }
+
+    // Parse the next chunk manually.
+    let mut index = [0; 4]; // maps to index in input
+    let mut index_len = 0;
+    let mut index_pad = 4;
+    let mut ipos = read;
+    let remaining = max_length - written;
+    if remaining == 0 {
+        return DecodeMutResult {
+            read,
+            written,
+            error: None,
+        };
+    }
+    while ipos < input.len() {
+        let byte = input[ipos];
+        let position = ipos;
+        ipos += 1;
+        let kind = match base.interpret_byte(byte) {
+            Character::Padding => unreachable!(),
+            Character::Ignored => continue,
+            Character::Symbol { .. } if index_pad < 4 => Some(DecodeKind::Padding),
+            Character::Symbol { .. } => None,
+            Character::Invalid if byte != b'=' => Some(DecodeKind::Symbol),
+            Character::Invalid if index_len < 2 => Some(DecodeKind::Padding),
+            Character::Invalid => {
+                index_pad = core::cmp::min(index_pad, index_len);
+                None
+            }
+        };
+        if let Some(kind) = kind {
+            return DecodeMutResult {
+                read,
+                written,
+                error: Some(DecodeError { position, kind }),
+            };
+        }
+        if index_len == 4 {
+            debug_assert!(index_pad < 4);
+            let error = Some(DecodeError {
+                position,
+                kind: DecodeKind::Padding,
+            });
+            return DecodeMutResult {
+                read,
+                written,
+                error,
+            };
+        }
+        index[index_len] = position;
+        index_len += 1;
+        if matches!(
+            (core::cmp::min(index_len, index_pad), remaining),
+            (3, 1) | (4, 2)
+        ) {
+            return DecodeMutResult {
+                read,
+                written,
+                error: None,
+            };
+        }
+    }
+    debug_assert!(index_len <= 4 && index_pad <= 4);
+    debug_assert!(index_len < 4 || index_pad < 4);
+
+    // Process the last chunk.
+    if index_len == 0 {
+        return DecodeMutResult {
+            read: input.len(),
+            written,
+            error: None,
+        };
+    }
+    let check = match (last_chunk_handling, index_len, index_pad) {
+        (Loose, 1, _) | (Loose, 0..4, 0..4) | (Strict, 0..4, _) => {
+            let error = Some(DecodeError {
+                position: ipos,
+                kind: DecodeKind::Length,
+            });
+            return DecodeMutResult {
+                read,
+                written,
+                error,
+            };
+        }
+        (Strict, _, _) => true,
+        (StopBeforePartial, 0..4, _) => {
+            return DecodeMutResult {
+                read,
+                written,
+                error: None,
+            };
+        }
+        (Loose | StopBeforePartial, _, _) => false,
+    };
+    let iend = core::cmp::min(index_len, index_pad);
+    let oend = iend - 1;
+    let mut ichunk = [b'A'; 4];
+    for i in 0..iend {
+        ichunk[i] = input[index[i]];
+    }
+    let mut ochunk = [0; 3];
+    let rchunk = base.decode_mut(&ichunk, &mut ochunk);
+    debug_assert_eq!(rchunk, Ok(3));
+    if check && iend < 4 && ochunk[oend] != 0 {
+        let error = Some(DecodeError {
+            position: index[iend],
+            kind: DecodeKind::Trailing,
+        });
+        return DecodeMutResult {
+            read,
+            written,
+            error,
+        };
+    }
+    output[written..][..oend].copy_from_slice(&ochunk[..oend]);
+    read = input.len();
+    written += oend;
+    DecodeMutResult {
+        read,
+        written,
+        error: None,
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) struct DecodeResult {
+    pub(crate) read: usize,
+    pub(crate) output: Vec<u8>,
+    pub(crate) error: Option<DecodeError>,
+}
+
+/// Decodes `input` in `output` according to the given parameters.
+pub(crate) fn decode(
+    input: &[u8],
+    alphabet: Alphabet,
+    last_chunk_handling: LastChunkHandling,
+    max_length: Option<usize>,
+) -> DecodeResult {
+    let mut output = vec![0; 6 * input.len() / 8];
+    let DecodeMutResult {
+        read,
+        written,
+        error,
+    } = decode_mut(
+        input,
+        &mut output,
+        alphabet,
+        last_chunk_handling,
+        max_length,
+    );
+    debug_assert!(written <= output.len());
+    output.truncate(written);
+    DecodeResult {
+        read,
+        output,
+        error,
+    }
+}
+
+pub(crate) fn encode(input: &[u8], alphabet: Alphabet, omit_padding: bool) -> String {
+    let base = match (alphabet, omit_padding) {
+        (Alphabet::Base64, false) => &data_encoding::BASE64,
+        (Alphabet::Base64, true) => &data_encoding::BASE64_NOPAD,
+        (Alphabet::Base64Url, false) => &data_encoding::BASE64URL,
+        (Alphabet::Base64Url, true) => &data_encoding::BASE64URL_NOPAD,
+    };
+
+    let mut output = String::with_capacity(base.encode_len(input.len()));
+    base.encode_append(input, &mut output);
+    output
+}
+
+const BASE64: Encoding = new_encoding! {
+    symbols: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
+    ignore: " \t\n\x0C\r",
+    check_trailing_bits: false,
+};
+
+const BASE64URL: Encoding = new_encoding! {
+    symbols: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
+    ignore: " \t\n\x0C\r",
+    check_trailing_bits: false,
+};