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Scanning a local file headers is not necessary (except in the case of corrupted archives) #451

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merged 3 commits into from
Mar 13, 2024
Merged

Scanning a local file headers is not necessary (except in the case of corrupted archives) #451

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ee5f98a
Update entryHeader.js
likev Mar 19, 2023
a137863
Scanning a local file headers is not necessary
likev Mar 19, 2023
ecfe95b
Merge pull request #1 from likev/patch-2
likev Mar 19, 2023
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59 changes: 40 additions & 19 deletions headers/entryHeader.js
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Original file line number Diff line number Diff line change
Expand Up @@ -168,39 +168,60 @@ module.exports = function () {
},

get realDataOffset() {
return _offset + Constants.LOCHDR + _dataHeader.fnameLen + _dataHeader.extraLen;
return _offset + Constants.LOCHDR + _fnameLen + _extraLen;
},

get dataHeader() {
return _dataHeader;
},

loadDataHeaderFromBinary: function (/*Buffer*/ input) {
var data = input.slice(_offset, _offset + Constants.LOCHDR);
// 30 bytes and should start with "PK\003\004"
if (data.readUInt32LE(0) !== Constants.LOCSIG) {
throw new Error(Utils.Errors.INVALID_LOC);
}
_dataHeader = {
// version needed to extract
version: data.readUInt16LE(Constants.LOCVER),
version: _version,
// general purpose bit flag
flags: data.readUInt16LE(Constants.LOCFLG),
flags: _flags,
// compression method
method: data.readUInt16LE(Constants.LOCHOW),
method: _method,
// modification time (2 bytes time, 2 bytes date)
time: data.readUInt32LE(Constants.LOCTIM),
time: _time,
// uncompressed file crc-32 value
crc: data.readUInt32LE(Constants.LOCCRC),
crc: _crc,
// compressed size
compressedSize: data.readUInt32LE(Constants.LOCSIZ),
compressedSize: _compressedSize,
// uncompressed size
size: data.readUInt32LE(Constants.LOCLEN),
size: _size,
// filename length
fnameLen: data.readUInt16LE(Constants.LOCNAM),
fnameLen: _fnameLen,
// extra field length
extraLen: data.readUInt16LE(Constants.LOCEXT)
extraLen: _extraLen
};

return _dataHeader;
},

loadDataHeaderFromBinary: function (/*Buffer*/ input) {
var data = input.slice(_offset, _offset + Constants.LOCHDR);
// 30 bytes and should start with "PK\003\004"
if (data.readUInt32LE(0) !== Constants.LOCSIG) {
throw new Error(Utils.Errors.INVALID_LOC);
}

// version needed to extract
_version = data.readUInt16LE(Constants.LOCVER);
// general purpose bit flag
_flags = data.readUInt16LE(Constants.LOCFLG);
// compression method
_method = data.readUInt16LE(Constants.LOCHOW);
// modification time (2 bytes time, 2 bytes date)
_time = data.readUInt32LE(Constants.LOCTIM);
// uncompressed file crc-32 value
_crc = data.readUInt32LE(Constants.LOCCRC);
// compressed size
_compressedSize = data.readUInt32LE(Constants.LOCSIZ);
// uncompressed size
_size = data.readUInt32LE(Constants.LOCLEN);
// filename length
_fnameLen = data.readUInt16LE(Constants.LOCNAM);
// extra field length
_extraLen = data.readUInt16LE(Constants.LOCEXT);

},

loadFromBinary: function (/*Buffer*/ data) {
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3 changes: 2 additions & 1 deletion zipEntry.js
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,8 @@ module.exports = function (/*Buffer*/ input) {
if (!input || !Buffer.isBuffer(input)) {
return Buffer.alloc(0);
}
_entryHeader.loadDataHeaderFromBinary(input);
//Scanning a local file headers is not necessary (except in the case of corrupted archives)
if(!_entryHeader.compressedSize) _entryHeader.loadDataHeaderFromBinary(input);
return input.slice(_entryHeader.realDataOffset, _entryHeader.realDataOffset + _entryHeader.compressedSize);
}

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