diff options
Diffstat (limited to 'node_modules/tar/lib/large-numbers.js')
-rw-r--r-- | node_modules/tar/lib/large-numbers.js | 97 |
1 files changed, 0 insertions, 97 deletions
diff --git a/node_modules/tar/lib/large-numbers.js b/node_modules/tar/lib/large-numbers.js deleted file mode 100644 index ad30bc3..0000000 --- a/node_modules/tar/lib/large-numbers.js +++ /dev/null @@ -1,97 +0,0 @@ -'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 |