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pub struct StyleWriterEncoder;
// StyleWriter Encoding Protocol Constants
pub const MAX_RUN: u8 = 0x3E;
pub const MAX_BLOCK: u8 = 0x3E;
pub const RUN_THRESH: u8 = 0x01;
pub const DATA_WHITE: u8 = 0x00;
pub const DATA_BLACK: u8 = 0xFF;
pub const MASK_RUNWHT: u8 = 0x80;
pub const MASK_RUNBLK: u8 = 0xC0;
impl StyleWriterEncoder {
/// Create the bounding box header (`R` for monochrome, `c` for color)
pub fn encode_rect(top: u16, left: u16, bottom: u16, right: u16, is_color: bool) -> Vec<u8> {
let mut buf = Vec::with_capacity(9);
if is_color {
buf.push(b'c');
} else {
buf.push(b'R');
}
buf.extend_from_slice(&left.to_le_bytes());
buf.extend_from_slice(&top.to_le_bytes());
buf.extend_from_slice(&right.to_le_bytes());
buf.extend_from_slice(&bottom.to_le_bytes());
buf
}
/// Prepend the Apple `'G'` 2-byte chunk sizes to an encoded RLE block
pub fn wrap_raster_chunk(encoded_data: &[u8]) -> Vec<u8> {
let size = encoded_data.len() as u16;
let mut buf = Vec::with_capacity(4 + size as usize);
buf.push(b'G');
buf.extend_from_slice(&size.to_le_bytes());
buf.extend_from_slice(encoded_data);
buf.push(0x00); // Null terminator required for G blocks
buf
}
/// Encode a single raw bitmap scanline into the proprietary Apple RLE format
/// Ported directly from lpstyl.c `encodescanline()`
pub fn encode_scanline(src: &[u8], print_width_bytes: usize) -> Vec<u8> {
let mut dst = Vec::with_capacity(src.len());
// SPECIAL CASE: Check for a completely blank line
if src.iter().all(|&b| b == DATA_WHITE) {
dst.push(MASK_RUNWHT);
return dst;
}
let mut s = 0;
let src_len = src.len();
while s < src_len {
let mut run_start = 0;
let mut run_len = 0;
let mut run_char = 0x0A; // DATA_OTHER (just not black or white)
// Find the first run
let mut found_break = false;
let mut i = s;
while i < src_len {
if run_char == DATA_WHITE || run_char == DATA_BLACK {
if src[i] != run_char {
// This run is over
if (i - run_start) >= RUN_THRESH as usize {
// Run was long enough to count. Break out.
found_break = true;
break;
} else {
run_char = 0x0A; // Too short to count.
}
} else if (i - run_start) >= MAX_RUN as usize {
// Enough of a run to encode
found_break = true;
break;
}
} else {
// run_char == DATA_OTHER
if src[i] == DATA_WHITE || src[i] == DATA_BLACK {
// Start a run
run_char = src[i];
run_start = i;
} else if (i - s) >= MAX_BLOCK as usize {
// Block is maximum length
found_break = true;
break;
}
}
i += 1;
}
if found_break || run_char != 0x0A {
if run_char != 0x0A {
run_len = i - run_start;
} else {
run_start = i;
}
} else {
run_start = i;
}
if run_start != s {
// Encode a run of random data
dst.push((run_start - s) as u8);
while s < run_start {
dst.push(src[s]);
s += 1;
}
}
if run_len > 0 {
// Encode a run of black or white
if run_char == DATA_BLACK {
dst.push(MASK_RUNBLK + run_len as u8);
} else if (s + run_len) < src_len {
dst.push(MASK_RUNWHT + run_len as u8);
} else {
break; // Let padding handle it
}
s += run_len;
}
}
// Pad out to the width of the page with white
while s < print_width_bytes {
let mut run_len = print_width_bytes - s;
if run_len > MAX_RUN as usize {
run_len = MAX_RUN as usize;
}
dst.push(MASK_RUNWHT + run_len as u8);
s += run_len;
}
dst
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_encode_rect() {
// R (0x52) or c (0x63), then little-endian left, top, right, bottom
let bw = StyleWriterEncoder::encode_rect(10, 20, 30, 40, false);
assert_eq!(bw, vec![b'R', 20, 0, 10, 0, 40, 0, 30, 0]);
let color = StyleWriterEncoder::encode_rect(10, 20, 30, 40, true);
assert_eq!(color, vec![b'c', 20, 0, 10, 0, 40, 0, 30, 0]);
}
#[test]
fn test_wrap_raster_chunk() {
let chunk = vec![0xAB, 0xCD, 0xEF];
let wrapped = StyleWriterEncoder::wrap_raster_chunk(&chunk);
assert_eq!(wrapped.len(), 7);
assert_eq!(wrapped[0], b'G');
assert_eq!(wrapped[1], 0x03); // Length LSB (3 bytes)
assert_eq!(wrapped[2], 0x00); // Length MSB
assert_eq!(&wrapped[3..6], &[0xAB, 0xCD, 0xEF]);
assert_eq!(wrapped.last(), Some(&0x00)); // Null terminator
}
#[test]
fn test_encode_scanline() {
// Test a pure white line (all 0s)
let white_line = vec![DATA_WHITE; 100];
let encoded = StyleWriterEncoder::encode_scanline(&white_line, 100);
assert_eq!(encoded, vec![MASK_RUNWHT]);
// Test a line padded with white at the end
let src = vec![DATA_BLACK, DATA_BLACK, DATA_BLACK]; // 3 black pixels
let encoded = StyleWriterEncoder::encode_scanline(&src, 10);
// Expect: MASK_RUNBLK + 3, MASK_RUNWHT + 7
assert_eq!(encoded, vec![MASK_RUNBLK + 3, MASK_RUNWHT + 7]);
// Test random data
let src = vec![0x11, 0x22, 0x33, DATA_WHITE, DATA_WHITE];
let encoded = StyleWriterEncoder::encode_scanline(&src, 5);
// Expect: random length 3 | 0x11 | 0x22 | 0x33 | then white pad/run
assert_eq!(encoded[0], 3); // 3 bytes of raw data
assert_eq!(&encoded[1..4], &[0x11, 0x22, 0x33]);
assert_eq!(encoded[4], MASK_RUNWHT + 2); // 2 bytes of white
}
}