diff options
author | Feross Aboukhadijeh <feross@feross.org> | 2013-10-26 11:57:53 +0400 |
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committer | Feross Aboukhadijeh <feross@feross.org> | 2013-10-26 11:57:53 +0400 |
commit | a64446d811fd9b5d676e7cb886a4e4f4072d99bb (patch) | |
tree | d724f7c63870e29aa868897db10f49ab60525044 /lib | |
parent | 40aa2dfd7660885ba1587e9fa591c608745a9832 (diff) |
chrome app that can send UDP packets to an echo server
Diffstat (limited to 'lib')
-rw-r--r-- | lib/string.js | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/lib/string.js b/lib/string.js new file mode 100644 index 0000000..80b1362 --- /dev/null +++ b/lib/string.js @@ -0,0 +1,90 @@ +/* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Base64_encoding_and_decoding */ + +exports.fromUTF8Arr = UTF8ArrToStr +exports.toUTF8Arr = strToUTF8Arr + +/* UTF-8 array to DOMString and vice versa */ + +function UTF8ArrToStr (aBytes) { + + var sView = ""; + + for (var nPart, nLen = aBytes.length, nIdx = 0; nIdx < nLen; nIdx++) { + nPart = aBytes[nIdx]; + sView += String.fromCharCode( + nPart > 251 && nPart < 254 && nIdx + 5 < nLen ? /* six bytes */ + /* (nPart - 252 << 32) is not possible in ECMAScript! So...: */ + (nPart - 252) * 1073741824 + (aBytes[++nIdx] - 128 << 24) + (aBytes[++nIdx] - 128 << 18) + (aBytes[++nIdx] - 128 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128 + : nPart > 247 && nPart < 252 && nIdx + 4 < nLen ? /* five bytes */ + (nPart - 248 << 24) + (aBytes[++nIdx] - 128 << 18) + (aBytes[++nIdx] - 128 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128 + : nPart > 239 && nPart < 248 && nIdx + 3 < nLen ? /* four bytes */ + (nPart - 240 << 18) + (aBytes[++nIdx] - 128 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128 + : nPart > 223 && nPart < 240 && nIdx + 2 < nLen ? /* three bytes */ + (nPart - 224 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128 + : nPart > 191 && nPart < 224 && nIdx + 1 < nLen ? /* two bytes */ + (nPart - 192 << 6) + aBytes[++nIdx] - 128 + : /* nPart < 127 ? */ /* one byte */ + nPart + ); + } + + return sView; + +} + +function strToUTF8Arr (sDOMStr) { + + var aBytes, nChr, nStrLen = sDOMStr.length, nArrLen = 0; + + /* mapping... */ + + for (var nMapIdx = 0; nMapIdx < nStrLen; nMapIdx++) { + nChr = sDOMStr.charCodeAt(nMapIdx); + nArrLen += nChr < 0x80 ? 1 : nChr < 0x800 ? 2 : nChr < 0x10000 ? 3 : nChr < 0x200000 ? 4 : nChr < 0x4000000 ? 5 : 6; + } + + aBytes = new Uint8Array(nArrLen); + + /* transcription... */ + + for (var nIdx = 0, nChrIdx = 0; nIdx < nArrLen; nChrIdx++) { + nChr = sDOMStr.charCodeAt(nChrIdx); + if (nChr < 128) { + /* one byte */ + aBytes[nIdx++] = nChr; + } else if (nChr < 0x800) { + /* two bytes */ + aBytes[nIdx++] = 192 + (nChr >>> 6); + aBytes[nIdx++] = 128 + (nChr & 63); + } else if (nChr < 0x10000) { + /* three bytes */ + aBytes[nIdx++] = 224 + (nChr >>> 12); + aBytes[nIdx++] = 128 + (nChr >>> 6 & 63); + aBytes[nIdx++] = 128 + (nChr & 63); + } else if (nChr < 0x200000) { + /* four bytes */ + aBytes[nIdx++] = 240 + (nChr >>> 18); + aBytes[nIdx++] = 128 + (nChr >>> 12 & 63); + aBytes[nIdx++] = 128 + (nChr >>> 6 & 63); + aBytes[nIdx++] = 128 + (nChr & 63); + } else if (nChr < 0x4000000) { + /* five bytes */ + aBytes[nIdx++] = 248 + (nChr >>> 24); + aBytes[nIdx++] = 128 + (nChr >>> 18 & 63); + aBytes[nIdx++] = 128 + (nChr >>> 12 & 63); + aBytes[nIdx++] = 128 + (nChr >>> 6 & 63); + aBytes[nIdx++] = 128 + (nChr & 63); + } else /* if (nChr <= 0x7fffffff) */ { + /* six bytes */ + aBytes[nIdx++] = 252 + /* (nChr >>> 32) is not possible in ECMAScript! So...: */ (nChr / 1073741824); + aBytes[nIdx++] = 128 + (nChr >>> 24 & 63); + aBytes[nIdx++] = 128 + (nChr >>> 18 & 63); + aBytes[nIdx++] = 128 + (nChr >>> 12 & 63); + aBytes[nIdx++] = 128 + (nChr >>> 6 & 63); + aBytes[nIdx++] = 128 + (nChr & 63); + } + } + + return aBytes; + +}
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