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Fix C2M compression occasionally losing the last byte

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This commit is contained in:
Eevee (Evelyn Woods) 2020-12-03 15:39:11 -07:00
parent fa18238e60
commit 89ae9aa4a3
1 changed files with 10 additions and 6 deletions
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16
js/format-c2g.js
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@ -1117,10 +1117,18 @@ function compress(buf) {
// If we found a match that's worth copying (i.e. shorter than just writing a data block), // If we found a match that's worth copying (i.e. shorter than just writing a data block),
// then do so // then do so
let do_copy = (best_length > 3); let do_copy = (best_length > 3);
// If we're not copying, add this byte to a pending data block /now/, so the next block can
// catch it if it happens to be the last byte
if (! do_copy) {
pending_data_length += 1;
p++;
}
// Write out any pending data block if necessary -- i.e. if we're about to write a copy // Write out any pending data block if necessary -- i.e. if we're about to write a copy
// block, if we're at the max size of a data block, or if this is the end of the data // block, if we're at the max size of a data block, or if this is the end of the data
if (pending_data_length > 0 && if (pending_data_length > 0 &&
(do_copy || pending_data_length === 127 || p === buf.byteLength - 1)) (do_copy || pending_data_length === 127 || p >= buf.byteLength))
{ {
outbytes[q] = pending_data_length; outbytes[q] = pending_data_length;
q++; q++;
@ -1131,6 +1139,7 @@ function compress(buf) {
pending_data_length = 0; pending_data_length = 0;
} }
// Finally, do a copy
if (do_copy) { if (do_copy) {
outbytes[q] = 0x80 + best_length; outbytes[q] = 0x80 + best_length;
outbytes[q + 1] = p - best_start; outbytes[q + 1] = p - best_start;
@ -1138,11 +1147,6 @@ function compress(buf) {
// Update p, noting that we might've done a copy into the future // Update p, noting that we might've done a copy into the future
p += best_length; p += best_length;
} }
else {
// Otherwise, add this to a pending data block
pending_data_length += 1;
p++;
}
// If we ever exceed the uncompressed length, don't even bother // If we ever exceed the uncompressed length, don't even bother
if (q > buf.byteLength) { if (q > buf.byteLength) {