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import { Buffer, writeAll } from "./buffer.ts";
import { stdin } from "./files.ts";
import { TextEncoder, TextDecoder } from "./text_encoding.ts";
import { Reader, EOF } from "./io.ts";
export type XevalFunc = (v: string) => void;
// Generate longest proper prefix which is also suffix array.
function createLPS(pat: Uint8Array): Uint8Array {
const lps = new Uint8Array(pat.length);
lps[0] = 0;
let prefixEnd = 0;
let i = 1;
while (i < lps.length) {
if (pat[i] == pat[prefixEnd]) {
prefixEnd++;
lps[i] = prefixEnd;
i++;
} else if (prefixEnd === 0) {
lps[i] = 0;
i++;
} else {
prefixEnd = pat[prefixEnd - 1];
}
}
return lps;
}
// TODO(kevinkassimo): Move this utility to deno_std.
// Import from there once doable.
// Read from reader until EOF and emit string chunks separated
// by the given delimiter.
async function* chunks(
reader: Reader,
delim: string
): AsyncIterableIterator<string> {
const encoder = new TextEncoder();
const decoder = new TextDecoder();
// Avoid unicode problems
const delimArr = encoder.encode(delim);
const delimLen = delimArr.length;
const delimLPS = createLPS(delimArr);
let inputBuffer = new Buffer();
const inspectArr = new Uint8Array(Math.max(1024, delimLen + 1));
// Modified KMP
let inspectIndex = 0;
let matchIndex = 0;
while (true) {
const result = await reader.read(inspectArr);
if (result === EOF) {
// Yield last chunk.
const lastChunk = inputBuffer.toString();
yield lastChunk;
return;
}
if ((result as number) < 0) {
// Discard all remaining and silently fail.
return;
}
const sliceRead = inspectArr.subarray(0, result as number);
await writeAll(inputBuffer, sliceRead);
let sliceToProcess = inputBuffer.bytes();
while (inspectIndex < sliceToProcess.length) {
if (sliceToProcess[inspectIndex] === delimArr[matchIndex]) {
inspectIndex++;
matchIndex++;
if (matchIndex === delimLen) {
// Full match
const matchEnd = inspectIndex - delimLen;
const readyBytes = sliceToProcess.subarray(0, matchEnd);
// Copy
const pendingBytes = sliceToProcess.slice(inspectIndex);
const readyChunk = decoder.decode(readyBytes);
yield readyChunk;
// Reset match, different from KMP.
sliceToProcess = pendingBytes;
inspectIndex = 0;
matchIndex = 0;
}
} else {
if (matchIndex === 0) {
inspectIndex++;
} else {
matchIndex = delimLPS[matchIndex - 1];
}
}
}
// Keep inspectIndex and matchIndex.
inputBuffer = new Buffer(sliceToProcess);
}
}
export async function xevalMain(
xevalFunc: XevalFunc,
delim_: string | null
): Promise<void> {
if (!delim_) {
delim_ = "\n";
}
for await (const chunk of chunks(stdin, delim_)) {
// Ignore empty chunks.
if (chunk.length > 0) {
xevalFunc(chunk);
}
}
}
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