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Ensure that TrueType font tables have uint32 checksums

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According to "The table directory" under https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6.html#Directory, TrueType font tables should have `uint32` checksums.

This is something that I noticed, and was initially confused about, while debugging a TrueType issue.
As far as I can tell, the current (`int32`) checksums we use doesn't cause any issues in practice. However, I do think that this should be addressed to agree with the specification, and to reduce possible confusion when reading the font code.
This commit is contained in:
Jonas Jenwald 2016-03-22 13:16:08 +01:00
parent 21ed8ff71d
commit d78fae0181
1 changed files with 3 additions and 4 deletions
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7
src/core/fonts.js
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@ -403,9 +403,8 @@ var OpenTypeFileBuilder = (function OpenTypeFileBuilderClosure() {
// checksum // checksum
var checksum = 0; var checksum = 0;
for (j = tableOffsets[i], jj = tableOffsets[i + 1]; j < jj; j += 4) { for (j = tableOffsets[i], jj = tableOffsets[i + 1]; j < jj; j += 4) {
var quad = (file[j] << 24) + (file[j + 1] << 16) + var quad = readUint32(file, j);
(file[j + 2] << 8) + file[j + 3]; checksum = (checksum + quad) >>> 0;
checksum = (checksum + quad) | 0;
} }
writeInt32(file, offset + 4, checksum); writeInt32(file, offset + 4, checksum);
@ -1246,7 +1245,7 @@ var Font = (function FontClosure() {
function readTableEntry(file) { function readTableEntry(file) {
var tag = bytesToString(file.getBytes(4)); var tag = bytesToString(file.getBytes(4));
var checksum = file.getInt32(); var checksum = file.getInt32() >>> 0;
var offset = file.getInt32() >>> 0; var offset = file.getInt32() >>> 0;
var length = file.getInt32() >>> 0; var length = file.getInt32() >>> 0;