71 lines
2.4 KiB
TypeScript
71 lines
2.4 KiB
TypeScript
export function str2ab8(str) {
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const buf = new ArrayBuffer(str.length);
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const bufView = new Uint8Array(buf);
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for (let i = 0, strLen = str.length; i < strLen; i++) {
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bufView[i] = str.charCodeAt(i);
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}
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return buf;
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}
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/* FIXME Dont use atob, because it sucks for non UTF-8 tings */
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export function arrayBufferBase64(base64: string) {
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base64 = atob(base64);
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const buf = new ArrayBuffer(base64.length);
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const bufView = new Uint8Array(buf);
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for (let i = 0, strLen = base64.length; i < strLen; i++) {
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bufView[i] = base64.charCodeAt(i);
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}
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return buf;
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}
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export function base64_encode_ab(source: ArrayBufferLike) {
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const encodings = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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let base64 = "";
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const bytes = new Uint8Array(source);
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const byte_length = bytes.byteLength;
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const byte_reminder = byte_length % 3;
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const main_length = byte_length - byte_reminder;
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let a, b, c, d;
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let chunk;
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// Main loop deals with bytes in chunks of 3
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for (let i = 0; i < main_length; i = i + 3) {
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// Combine the three bytes into a single integer
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chunk = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
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// Use bitmasks to extract 6-bit segments from the triplet
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a = (chunk & 16515072) >> 18; // 16515072 = (2^6 - 1) << 18
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b = (chunk & 258048) >> 12; // 258048 = (2^6 - 1) << 12
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c = (chunk & 4032) >> 6; // 4032 = (2^6 - 1) << 6
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d = (chunk & 63) >> 0; // 63 = (2^6 - 1) << 0
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// Convert the raw binary segments to the appropriate ASCII encoding
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base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
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}
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// Deal with the remaining bytes and padding
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if (byte_reminder == 1) {
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chunk = bytes[main_length];
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a = (chunk & 252) >> 2; // 252 = (2^6 - 1) << 2
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// Set the 4 least significant bits to zero
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b = (chunk & 3) << 4; // 3 = 2^2 - 1
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base64 += encodings[a] + encodings[b] + '==';
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} else if (byte_reminder == 2) {
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chunk = (bytes[main_length] << 8) | bytes[main_length + 1];
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a = (chunk & 64512) >> 10; // 64512 = (2^6 - 1) << 10
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b = (chunk & 1008) >> 4; // 1008 = (2^6 - 1) << 4
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// Set the 2 least significant bits to zero
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c = (chunk & 15) << 2; // 15 = 2^4 - 1
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base64 += encodings[a] + encodings[b] + encodings[c] + '=';
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}
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return base64
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} |