Created
October 5, 2011 11:00
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Binary calculations in JavaScript (checksum byte computation)
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta http-equiv="content-type" content="text/html; charset=UTF-8" /> | |
| <script> | |
| function E(id) { | |
| return document.getElementById(id); | |
| } | |
| window.onload = function () { | |
| var bytesField = E('bytes'), | |
| nibblesField = E('nibbles'), | |
| bytesChecksumField = E('bytes-checksum'); | |
| nibblesChecksumField = E('nibbles-checksum'); | |
| function calculateChecksum() { | |
| var bytes = bytesField.value, | |
| nibbles = nibblesField.value, | |
| bytesChecksum = 0, | |
| nibblesChecksum = 0, | |
| bytesCount = Math.floor(bytes.length / 2), | |
| nibblesCount = nibbles.length, | |
| i, b, offs; | |
| for (i = 0; i < bytesCount; i++) { | |
| offs = i * 2; | |
| b = parseInt(bytes[offs] + bytes[offs + 1], 16); | |
| bytesChecksum = (bytesChecksum ^ b) & 0xFF; | |
| } | |
| for (i = 0; i < nibblesCount; i++) { | |
| b = parseInt(nibbles[i], 16); | |
| nibblesChecksum = (nibblesChecksum ^ b) & 0xFF; | |
| } | |
| if (bytes == '') { | |
| bytesChecksumField.value = ''; | |
| } else { | |
| bytesChecksumField.value = bytesChecksum.toString(16).toUpperCase(); | |
| } | |
| if (nibbles == '') { | |
| nibblesChecksumField.value = ''; | |
| } else { | |
| nibblesChecksumField.value = nibblesChecksum.toString(16); | |
| } | |
| if (bytesChecksumField.value.length === 1) { | |
| bytesChecksumField.value = '0' + bytesChecksumField.value; | |
| } | |
| } | |
| E('convert').onclick = calculateChecksum; | |
| bytesField.onchange = calculateChecksum; | |
| bytesField.onkeyup = calculateChecksum; | |
| nibblesField.onchange = calculateChecksum; | |
| nibblesField.onkeyup = calculateChecksum; | |
| bytesField.onfocus = function () { this.select(); }; | |
| nibblesField.onfocus = function () { this.select(); }; | |
| bytesChecksumField.onfocus = function () { this.select(); }; | |
| }; | |
| </script> | |
| </head> | |
| <body> | |
| Байтове:<br /> | |
| <textarea id="bytes" rows="4" cols="80"></textarea><br /> | |
| Nibbles:<br /> | |
| <textarea id="nibbles" rows="4" cols="80"></textarea><br /> | |
| <input type="button" id="convert" value="Пресметнете сумата ↓" /><br /> | |
| Байтова контролна сума: <input type="text" id="bytes-checksum" size="20" readonly="readonly" /><br /> | |
| Nibble-контролна сума: <input type="text" id="nibbles-checksum" size="20" readonly="readonly" /> | |
| </body> | |
| </html> |
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