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39 lines
1.3 KiB
39 lines
1.3 KiB
10 years ago
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/*
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* Helper to check if a number is internally represented as a fastint:
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*
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* if (Duktape.isFastint(x)) {
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* print('fastint');
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* } else {
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* print('not a fastint (or not a number)');
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* }
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*
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* NOTE: This helper depends on the internal tag numbering (defined in
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* duk_tval.h) which is both version specific and depends on whether
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* duk_tval is packed or not.
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*/
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if (typeof Duktape === 'object') {
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if (typeof Duktape.fastintTag === 'undefined') {
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Object.defineProperty(Duktape, 'fastintTag', {
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/* Tag number depends on duk_tval packing. */
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value: (Duktape.info(true)[1] === 0xfff4) ?
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0xfff1 /* tag for packed duk_tval */ :
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1 /* tag for unpacked duk_tval */,
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writable: false,
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enumerable: false,
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configurable: true
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});
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}
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if (typeof Duktape.isFastint === 'undefined') {
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Object.defineProperty(Duktape, 'isFastint', {
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value: function (v) {
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return Duktape.info(v)[0] === 4 && /* public type is DUK_TYPE_NUMBER */
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Duktape.info(v)[1] === Duktape.fastintTag; /* internal tag is fastint */
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},
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writable: false,
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enumerable: false,
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configurable: true
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});
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}
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}
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