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author | 2020-11-16 00:10:28 +0100 | |
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committer | 2020-11-16 00:10:28 +0100 | |
commit | e06ec920f7a5d784e674c4c4b4e6d1da3dc7391d (patch) | |
tree | 55713f725f77b44ebfec86e4eec3ce33e71458ca /node_modules/tar/lib/large-numbers.js | |
download | website_creator-e06ec920f7a5d784e674c4c4b4e6d1da3dc7391d.tar.gz website_creator-e06ec920f7a5d784e674c4c4b4e6d1da3dc7391d.tar.bz2 website_creator-e06ec920f7a5d784e674c4c4b4e6d1da3dc7391d.zip |
api, login, auth
Diffstat (limited to 'node_modules/tar/lib/large-numbers.js')
-rw-r--r-- | node_modules/tar/lib/large-numbers.js | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/node_modules/tar/lib/large-numbers.js b/node_modules/tar/lib/large-numbers.js new file mode 100644 index 0000000..ad30bc3 --- /dev/null +++ b/node_modules/tar/lib/large-numbers.js @@ -0,0 +1,97 @@ +'use strict' +// Tar can encode large and negative numbers using a leading byte of +// 0xff for negative, and 0x80 for positive. + +const encode = exports.encode = (num, buf) => { + if (!Number.isSafeInteger(num)) + // The number is so large that javascript cannot represent it with integer + // precision. + throw Error('cannot encode number outside of javascript safe integer range') + else if (num < 0) + encodeNegative(num, buf) + else + encodePositive(num, buf) + return buf +} + +const encodePositive = (num, buf) => { + buf[0] = 0x80 + + for (var i = buf.length; i > 1; i--) { + buf[i-1] = num & 0xff + num = Math.floor(num / 0x100) + } +} + +const encodeNegative = (num, buf) => { + buf[0] = 0xff + var flipped = false + num = num * -1 + for (var i = buf.length; i > 1; i--) { + var byte = num & 0xff + num = Math.floor(num / 0x100) + if (flipped) + buf[i-1] = onesComp(byte) + else if (byte === 0) + buf[i-1] = 0 + else { + flipped = true + buf[i-1] = twosComp(byte) + } + } +} + +const parse = exports.parse = (buf) => { + var post = buf[buf.length - 1] + var pre = buf[0] + var value; + if (pre === 0x80) + value = pos(buf.slice(1, buf.length)) + else if (pre === 0xff) + value = twos(buf) + else + throw Error('invalid base256 encoding') + + if (!Number.isSafeInteger(value)) + // The number is so large that javascript cannot represent it with integer + // precision. + throw Error('parsed number outside of javascript safe integer range') + + return value +} + +const twos = (buf) => { + var len = buf.length + var sum = 0 + var flipped = false + for (var i = len - 1; i > -1; i--) { + var byte = buf[i] + var f + if (flipped) + f = onesComp(byte) + else if (byte === 0) + f = byte + else { + flipped = true + f = twosComp(byte) + } + if (f !== 0) + sum -= f * Math.pow(256, len - i - 1) + } + return sum +} + +const pos = (buf) => { + var len = buf.length + var sum = 0 + for (var i = len - 1; i > -1; i--) { + var byte = buf[i] + if (byte !== 0) + sum += byte * Math.pow(256, len - i - 1) + } + return sum +} + +const onesComp = byte => (0xff ^ byte) & 0xff + +const twosComp = byte => ((0xff ^ byte) + 1) & 0xff |