blind

commit f757761b310a899dc8ece7ad7845ed0a22ff752b
parent 2debbbe6e70b66357fa510850b57c47406a87249
Author: Mattias Andrée <maandree@kth.se>
Date:   Thu, 26 Jan 2017 07:26:42 +0100

Add blind-compress and blind-decompress

Signed-off-by: Mattias Andrée <maandree@kth.se>

Diffstat:
A
src/blind-compress.c
 | 
69
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
src/blind-decompress.c
 | 
64
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 133 insertions(+), 0 deletions(-)
diff --git a/src/blind-compress.c b/src/blind-compress.c
@@ -0,0 +1,69 @@
+/* See LICENSE file for copyright and license details. */
+#include "stream.h"
+#include "util.h"
+
+#include <string.h>
+#include <unistd.h>
+
+USAGE("")
+
+static size_t
+compare(const char *restrict new, const char *restrict old, size_t n, size_t **cmp, size_t *cmpsize)
+{
+	size_t i, start1, start2, ptr, same, diff;
+	for (ptr = i = 0; i < n;) {
+		for (start1 = i; i < n && old[i] == new[i]; i++);
+		for (start2 = i; i < n && old[i] != new[i]; i++);
+		same = start2 - start1;
+		diff = i - start2;
+		if (ptr && same < 2 * sizeof(size_t) && same + diff <= SIZE_MAX - (*cmp)[ptr - 1]) {
+			(*cmp)[ptr - 1] += same + diff;
+		} else {
+			if (ptr + 2 > *cmpsize)
+				*cmp = erealloc(*cmp, (*cmpsize += 128) * sizeof(size_t));
+			(*cmp)[ptr++] = same;
+			(*cmp)[ptr++] = diff;
+		}
+	}
+	return ptr;
+}
+
+int
+main(int argc, char *argv[])
+{
+	struct stream stream;
+	char *buf[2];
+	size_t n, parts, part, off;
+	int i;
+	size_t *cmp = NULL;
+	size_t cmpsize = 0;
+
+	ENOFLAGS(argc);
+
+	stream.file = "<stdin>";
+	stream.fd = STDIN_FILENO;
+	einit_stream(&stream);
+	fprint_stream_head(stdout, &stream);
+	efflush(stdout, "<stdout>");
+
+	echeck_frame_size(stream.width, stream.height, stream.pixel_size, 0, "<stdin>");
+	n = stream.width * stream.height * stream.pixel_size;
+	buf[0] = emalloc(n);
+	buf[1] = ecalloc(1, n);
+
+	memcpy(buf[0], stream.buf, stream.ptr);
+	for (i = 0; eread_frame(&stream, buf[i], n); i ^= 1) {
+		parts = compare(buf[i], buf[i ^ 1], n, &cmp, &cmpsize);
+		for (off = part = 0; part < parts; part += 2) {
+			off += cmp[part];
+			ewriteall(STDOUT_FILENO, cmp + part, 2 * sizeof(size_t), "<stdout>");
+			ewriteall(STDOUT_FILENO, buf[i] + off, cmp[part + 1], "<stdout>");
+			off += cmp[part + 1];
+		}
+	}
+
+	free(cmp);
+	free(buf[0]);
+	free(buf[1]);
+	return 0;
+}
diff --git a/src/blind-decompress.c b/src/blind-decompress.c
@@ -0,0 +1,64 @@
+/* See LICENSE file for copyright and license details. */
+#include "stream.h"
+#include "util.h"
+
+#include <string.h>
+#include <unistd.h>
+
+USAGE("")
+
+int
+main(int argc, char *argv[])
+{
+	struct stream stream;
+	char *buf;
+	size_t n, m, fptr, sptr, same = 0, diff = 0;
+
+	ENOFLAGS(argc);
+
+	stream.file = "<stdin>";
+	stream.fd = STDIN_FILENO;
+	einit_stream(&stream);
+	fprint_stream_head(stdout, &stream);
+	efflush(stdout, "<stdout>");
+
+	echeck_frame_size(stream.width, stream.height, stream.pixel_size, 0, "<stdin>");
+	n = stream.width * stream.height * stream.pixel_size;
+	buf = ecalloc(1, n);
+
+	fptr = 0;
+	do {
+		sptr = 0;
+	again:
+		while (same) {
+			m = same < n - fptr ? same : n - fptr;
+			ewriteall(STDOUT_FILENO, buf + fptr, m, "<stdout>");
+			fptr = (fptr + m) % n;
+			same -= m;
+		}
+
+		while (diff && sptr < stream.ptr) {
+			m = diff < n - fptr ? diff : n - fptr;
+			m = m < stream.ptr - sptr ? m : stream.ptr - sptr;
+			memcpy(buf + fptr, stream.buf + sptr, m);
+			ewriteall(STDOUT_FILENO, buf + fptr, m, "<stdout>");
+			fptr = (fptr + m) % n;
+			diff -= m;
+			sptr += m;
+		}
+
+		if (diff || sptr + 2 * sizeof(size_t) > stream.ptr) {
+			memmove(stream.buf, stream.buf + sptr, stream.ptr -= sptr);
+		} else {
+			same = ((size_t *)(stream.buf + sptr))[0];
+			diff = ((size_t *)(stream.buf + sptr))[1];
+			sptr += 2 * sizeof(size_t);
+			goto again;
+		}
+	} while (eread_stream(&stream, SIZE_MAX));
+
+	free(buf);
+	if (same || diff)
+		eprintf("<stdin>: corrupt input\n");
+	return 0;
+}