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- var base64 = require('./base64');
- var VLQ_BASE_SHIFT = 5;
- var VLQ_BASE = 1 << VLQ_BASE_SHIFT;
- var VLQ_BASE_MASK = VLQ_BASE - 1;
- var VLQ_CONTINUATION_BIT = VLQ_BASE;
- function toVLQSigned(aValue) {
- return aValue < 0
- ? ((-aValue) << 1) + 1
- : (aValue << 1) + 0;
- }
- function fromVLQSigned(aValue) {
- var isNegative = (aValue & 1) === 1;
- var shifted = aValue >> 1;
- return isNegative
- ? -shifted
- : shifted;
- }
- exports.encode = function base64VLQ_encode(aValue) {
- var encoded = "";
- var digit;
- var vlq = toVLQSigned(aValue);
- do {
- digit = vlq & VLQ_BASE_MASK;
- vlq >>>= VLQ_BASE_SHIFT;
- if (vlq > 0) {
-
-
- digit |= VLQ_CONTINUATION_BIT;
- }
- encoded += base64.encode(digit);
- } while (vlq > 0);
- return encoded;
- };
- exports.decode = function base64VLQ_decode(aStr, aIndex, aOutParam) {
- var strLen = aStr.length;
- var result = 0;
- var shift = 0;
- var continuation, digit;
- do {
- if (aIndex >= strLen) {
- throw new Error("Expected more digits in base 64 VLQ value.");
- }
- digit = base64.decode(aStr.charCodeAt(aIndex++));
- if (digit === -1) {
- throw new Error("Invalid base64 digit: " + aStr.charAt(aIndex - 1));
- }
- continuation = !!(digit & VLQ_CONTINUATION_BIT);
- digit &= VLQ_BASE_MASK;
- result = result + (digit << shift);
- shift += VLQ_BASE_SHIFT;
- } while (continuation);
- aOutParam.value = fromVLQSigned(result);
- aOutParam.rest = aIndex;
- };
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