feat(std/io): Export readDelim(), readStringDelim() and readLines() from bufio.ts (#4019)

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

1 files changed, 9 insertions, 95 deletions

diff --git a/std/examples/xeval.ts b/std/examples/xeval.ts
index 75c864745..16ce37fb4 100644
--- a/std/examples/xeval.ts
+++ b/std/examples/xeval.ts
@@ -1,5 +1,6 @@
 import { parse } from "../flags/mod.ts";
-const { Buffer, EOF, args, exit, stdin, writeAll } = Deno;
+import { readStringDelim } from "../io/bufio.ts";
+const { args, exit, stdin } = Deno;
 type Reader = Deno.Reader;
 
 /* eslint-disable-next-line max-len */
@@ -10,18 +11,16 @@ const AsyncFunction = Object.getPrototypeOf(async function(): Promise<void> {})
 /* eslint-disable max-len */
 const HELP_MSG = `xeval
 
-Eval a script on lines from stdin.
-Read from standard input and eval code on each whitespace-delimited
-string chunks.
+Run a script for each new-line or otherwise delimited chunk of standard input.
 
 Print all the usernames in /etc/passwd:
-  cat /etc/passwd | deno -A https://deno.land/std/examples/xeval.ts -- "a = $.split(':'); if (a) console.log(a[0])"
+  cat /etc/passwd | deno -A https://deno.land/std/examples/xeval.ts "a = $.split(':'); if (a) console.log(a[0])"
 
 A complicated way to print the current git branch:
-  git branch | deno -A https://deno.land/std/examples/xeval.ts -- -I 'line' "if (line.startsWith('*')) console.log(line.slice(2))"
+  git branch | deno -A https://deno.land/std/examples/xeval.ts -I 'line' "if (line.startsWith('*')) console.log(line.slice(2))"
 
 Demonstrates breaking the input up by space delimiter instead of by lines:
-  cat LICENSE | deno -A https://deno.land/std/examples/xeval.ts -- -d " " "if ($ === 'MIT') console.log('MIT licensed')",
+  cat LICENSE | deno -A https://deno.land/std/examples/xeval.ts -d " " "if ($ === 'MIT') console.log('MIT licensed')",
 
 USAGE:
   deno -A https://deno.land/std/examples/xeval.ts [OPTIONS] <code>
@@ -40,98 +39,12 @@ export interface XevalOptions {
 
 const DEFAULT_DELIMITER = "\n";
 
-// 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;
-}
-
-// 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 xeval(
   reader: Reader,
   xevalFunc: XevalFunc,
   { delimiter = DEFAULT_DELIMITER }: XevalOptions = {}
 ): Promise<void> {
-  for await (const chunk of chunks(reader, delimiter)) {
+  for await (const chunk of readStringDelim(reader, delimiter)) {
     // Ignore empty chunks.
     if (chunk.length > 0) {
       await xevalFunc(chunk);
@@ -140,7 +53,7 @@ export async function xeval(
 }
 
 async function main(): Promise<void> {
-  const parsedArgs = parse(args.slice(1), {
+  const parsedArgs = parse(args, {
     boolean: ["help"],
     string: ["delim", "replvar"],
     alias: {
@@ -155,6 +68,7 @@ async function main(): Promise<void> {
   });
   if (parsedArgs._.length != 1) {
     console.error(HELP_MSG);
+    console.log(parsedArgs._);
     exit(1);
   }
   if (parsedArgs.help) {