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/* Wrapper for accessing strings through sequential reads */
function Stream(str) {
var position = 0;
function read(length) {
var result = str.substr(position, length);
position += length;
return result;
}
/* read a big-endian 32-bit integer */
function readInt32() {
var result = (
(str.charCodeAt(position) << 24)
+ (str.charCodeAt(position + 1) << 16)
+ (str.charCodeAt(position + 2) << 8)
+ str.charCodeAt(position + 3));
position += 4;
return result;
}
/* read a big-endian 16-bit integer */
function readInt16() {
var result = (
(str.charCodeAt(position) << 8)
+ str.charCodeAt(position + 1));
position += 2;
return result;
}
/* read an 8-bit integer */
function readInt8(signed) {
var result = str.charCodeAt(position);
if (signed && result > 127) result -= 256;
position += 1;
return result;
}
function eof() {
return position >= str.length;
}
/* read a MIDI-style variable-length integer
(big-endian value in groups of 7 bits,
with top bit set to signify that another byte follows)
*/
function readVarInt() {
var result = 0;
while (true) {
var b = readInt8();
if (b & 0x80) {
result += (b & 0x7f);
result <<= 7;
} else {
/* b is the last byte */
return result + b;
}
}
}
return {
'eof': eof,
'read': read,
'readInt32': readInt32,
'readInt16': readInt16,
'readInt8': readInt8,
'readVarInt': readVarInt
}
}
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