/prog/ - post you are run length encoding in lisp

Name: Anonymous 2014-10-05 3:18

critique mine pl0x:

(defun rle (str) ;run length encoding
  (let ((i 0) c count out)
    (while (< i (length str))
      (if (eq c (elt str i))
	  (setq count (1+ count))
	(when c
	  (setq out (append out (list (cons c count)))))
	(setq c (elt str i))
	(setq count 1))
      (setq i (1+ i)))
    (when c (setq out (append out (list (cons c count)))))
    out))

Name: Anonymous 2014-10-09 7:43

rle:

#include <stdio.h>

int main(int argc, char **argv) {
	int byte, count, temp;
begin:
	byte = getchar();
	count = 0;
	if (byte == EOF) return 0;
is_same:
	temp = getchar();
	if (temp == EOF) {
		putchar(count); putchar(byte);
		return 0;
	} else if (byte == temp) {
		count++;
		if (count == 255) {
			putchar(count); putchar(byte);
			goto begin;
		} else goto is_same;
	} else {
		putchar(count); putchar(byte);
		byte = temp; count = 0;
		goto is_same;
	}
}

unrle:

#include <stdio.h>

int main(int argc, char **argv) {
	int count, byte;
	for (;;) {
		count = getchar();
		byte = getchar();
		if (count == EOF || byte == EOF) return 0;
		for (int i = 0; i <= count; i++) putchar(byte);
	}
}

Name: Anonymous 2014-10-09 9:27

>>50
rle in memory:

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
typedef uint8_t u8;

/* Run-length encodes data, returning the malloc-allocated buffer in ebytes
   and its size in esize. */
void rle(u8 *ubytes, size_t usize, u8 **ebytes, size_t *esize) {
	// rle can double the input size in the worst case
	u8 *eb = malloc(usize * 2);
	size_t ui = 0;
	size_t ei = 0;
	u8 byte, count;

begin:
	byte = ubytes[ui];
	count = 0;
is_same:
	ui++;
	if (ui == usize) {
		eb[ei++] = count;
		eb[ei++] = byte;
		*esize = ei;
		*ebytes = malloc(ei);
		memcpy(*ebytes, eb, ei);
		free(eb);
		return;
	} else if (byte == ubytes[ui]) {
		count++;
		if (count == 255) goto write;
		goto is_same;
	} else {
write:
		eb[ei++] = count;
		eb[ei++] = byte;
		goto begin;
	}
}

unrle in memory:

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
typedef uint8_t u8;

/* Decompresses run-length encoded data, returning the data in ubytes
   and its size in usize */
void unrle(u8 *ebytes, size_t esize, u8 **ubytes, size_t *usize) {
	// unrle can expand the input 256-fold in the best case
	u8 *ub = malloc(esize * 256);
	size_t ei, ui;
	u8 count, byte;
	for (ei = 0, ui = 0; ei < esize;) {
		count = ebytes[ei++];
		byte = ebytes[ei++];
		for (int i = 0; i <= count; i++) ub[ui++] = byte;
	}
	
	*ubytes = malloc(ui);
	*usize = ui;
	memcpy(*ubytes, ub, ui);
	free(ub);
	return;
}

post you are run length encoding in lisp

1 Name: Anonymous 2014-10-05 3:18

50 Name: Anonymous 2014-10-09 7:43

54 Name: Anonymous 2014-10-09 9:27

Name: Anonymous 2014-10-05 3:18

Name: Anonymous 2014-10-09 7:43

Name: Anonymous 2014-10-09 9:27