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write out the rest of the encode cases

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pharpend
2022-10-19 03:17:49 -06:00
parent 7fe7e1cc2b
commit 0f1a181c08
1 changed files with 87 additions and 14 deletions
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bindings/typescript/src/base64.ts
+87 -14
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@@ -99,21 +99,21 @@ encode3(bytes: Uint8Array) {
// ABCDEF GH1234 5678AB CDEFGH
// n0 n1 n2 n3
let n0 : number = b0 >> 2;
// n1 = 00GH1234
// n1 = __GH1234
// b0 = ABCDEFGH
// 4 = 00000100
// b0 % 4 = 000000GH
// (b0 % 4) << 4 = 00GH0000
// 4 = _____1__
// b0 % 4 = ______GH
// (b0 % 4) << 4 = __GH____
// b1 = 12345678
// b1 >> 4 = 00001234
// b1 >> 4 = ____1234
let n1 : number = ((b0 % 4) << 4) + (b1 >> 4);
// n2 = 005678AB
// n2 = __5678AB
// b1 = 12345678
// 16 = 00010000
// b1 % 16 = 00005678
// (b1 % 16) << 2 = 00567800
// 16 = ___1____
// b1 % 16 = ____5678
// (b1 % 16) << 2 = __5678__
// b1 = ABCDEFGH
// b1 >> 6 = 000000AB
// b1 >> 6 = ______AB
let n2 : number = ((b1 % 16) << 2) + (b1 >> 6);
// n3 = 00CDEFGH
// 64 = 01000000
@@ -135,15 +135,88 @@ encode3(bytes: Uint8Array) {
/**
* Encode the final 0, 1, or 2 bytes
*
* FIXME: nyi
* @internal
*/
function
encode_tail(tail_bytes : Uint8Array,
tail_len : number)
: string
{
throw new Error('nyi');
: string {
switch(tail_len) {
case 0: return '';
case 1: return encode1(tail_bytes);
case 2: return encode2(tail_bytes);
default:
throw new Error('encode_tail with tail_len = ' + tail_len);
}
}
/**
* Encode a single byte
*
* @internal
*/
function
encode1(bytes: Uint8Array): string {
let b0 : number = bytes[0];
// n0 = __ABCDEF
// b0 = ABCDEFGH
// b0 >> 2 = __ABCDEF
let n0 : number = b0 >> 2;
// n1 = __GH____
// b0 = ABCDEFGH
// 4 = _____1__
// b0 % 4 = ______GH
// (b0 % 4) << 4 = __GH____
let n1 : number = (b0 % 4) << 4;
return int2char(n0) + int2char(n1) + '==';
}
/**
* Encode two bytes
*
* @internal
*/
function
encode2(bytes: Uint8Array): string {
return int2char(n0) + int2char(n1) + '==';
let b0 : number = bytes[0];
let b1 : number = bytes[1];
// ABCDEFGH 12345678
// b0 b1
// ABCDEF GH1234 5678__
// n0 n1 n2
let n0 : number = b0 >> 2;
// n1 = __GH1234
// b0 = ABCDEFGH
// 4 = _____1__
// b0 % 4 = ______GH
// (b0 % 4) << 4 = __GH____
// b1 = 12345678
// b1 >> 4 = ____1234
let n1 : number = ((b0 % 4) << 4) + (b1 >> 4);
// n2 = __5678AB
// b1 = 12345678
// 16 = ___1____
// b1 % 16 = ____5678
// (b1 % 16) << 2 = __5678__
let n2 : number = (b1 % 16) << 2;
// convert to chars
let s0 : string = int2char(n0);
let s1 : string = int2char(n1);
let s2 : string = int2char(n2);
// retrvn
return s0 + s1 + s2 + '=';
}
/**
* Conversion table for base64 encode