libio: remove buffer_offset from istream_t

Instead, make the buffer const, let the user adjust the pointer and
size. The offset can then be inferred in precache.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

12 files changed, 96 insertions, 107 deletions

diff --git a/lib/io/src/get_line.c b/lib/io/src/get_line.c
index f7e0b59..19af208 100644
--- a/lib/io/src/get_line.c
+++ b/lib/io/src/get_line.c
@@ -41,8 +41,8 @@ static size_t trim(char *buffer, int flags)
 int istream_get_line(istream_t *strm, char **out,
 		     size_t *line_num, int flags)
 {
+	size_t i, count, line_len = 0;
 	char *line = NULL, *new;
-	size_t i, line_len = 0;
 	bool have_line = false;
 
 	*out = NULL;
@@ -70,24 +70,28 @@ int istream_get_line(istream_t *strm, char **out,
 		}
 
 		if (i < strm->buffer_used) {
-			have_line = true;
-			strm->buffer_offset = i + 1;
+			count = i++;
+
+			if (count > 0 && strm->buffer[count - 1] == '\r')
+				--count;
 
-			if (i > 0 && strm->buffer[i - 1] == '\r')
-				--i;
+			have_line = true;
 		} else {
-			strm->buffer_offset = i;
+			count = i;
 		}
 
-		new = realloc(line, line_len + i + 1);
+		new = realloc(line, line_len + count + 1);
 		if (new == NULL)
 			goto fail_errno;
 
 		line = new;
-		memcpy(line + line_len, strm->buffer, i);
-		line_len += i;
+		memcpy(line + line_len, strm->buffer, count);
+		line_len += count;
 		line[line_len] = '\0';
 
+		strm->buffer += i;
+		strm->buffer_used -= i;
+
 		if (have_line) {
 			line_len = trim(line, flags);
 
diff --git a/lib/io/src/internal.h b/lib/io/src/internal.h
index 25a0196..1e51012 100644
--- a/lib/io/src/internal.h
+++ b/lib/io/src/internal.h
@@ -21,6 +21,7 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <assert.h>
 #include <ctype.h>
 #include <fcntl.h>
 #include <errno.h>
diff --git a/lib/io/src/istream.c b/lib/io/src/istream.c
index 2b89a00..0739fd6 100644
--- a/lib/io/src/istream.c
+++ b/lib/io/src/istream.c
@@ -16,7 +16,7 @@ sqfs_s32 istream_read(istream_t *strm, void *data, size_t size)
 		size = 0x7FFFFFFF;
 
 	while (size > 0) {
-		if (strm->buffer_offset >= strm->buffer_used) {
+		if (strm->buffer_used == 0) {
 			if (istream_precache(strm))
 				return -1;
 
@@ -24,13 +24,14 @@ sqfs_s32 istream_read(istream_t *strm, void *data, size_t size)
 				break;
 		}
 
-		diff = strm->buffer_used - strm->buffer_offset;
+		diff = strm->buffer_used;
 		if (diff > size)
 			diff = size;
 
-		memcpy(data, strm->buffer + strm->buffer_offset, diff);
+		memcpy(data, strm->buffer, diff);
 		data = (char *)data + diff;
-		strm->buffer_offset += diff;
+		strm->buffer += diff;
+		strm->buffer_used -= diff;
 		size -= diff;
 		total += diff;
 	}
@@ -43,7 +44,7 @@ int istream_skip(istream_t *strm, sqfs_u64 size)
 	size_t diff;
 
 	while (size > 0) {
-		if (strm->buffer_offset >= strm->buffer_used) {
+		if (strm->buffer_used == 0) {
 			if (istream_precache(strm))
 				return -1;
 
@@ -54,11 +55,12 @@ int istream_skip(istream_t *strm, sqfs_u64 size)
 			}
 		}
 
-		diff = strm->buffer_used - strm->buffer_offset;
+		diff = strm->buffer_used;
 		if ((sqfs_u64)diff > size)
 			diff = size;
 
-		strm->buffer_offset += diff;
+		strm->buffer += diff;
+		strm->buffer_used -= diff;
 		size -= diff;
 	}
 
@@ -74,7 +76,7 @@ sqfs_s32 istream_splice(istream_t *in, ostream_t *out, sqfs_u32 size)
 		size = 0x7FFFFFFF;
 
 	while (size > 0) {
-		if (in->buffer_offset >= in->buffer_used) {
+		if (in->buffer_used == 0) {
 			if (istream_precache(in))
 				return -1;
 
@@ -82,14 +84,15 @@ sqfs_s32 istream_splice(istream_t *in, ostream_t *out, sqfs_u32 size)
 				break;
 		}
 
-		diff = in->buffer_used - in->buffer_offset;
+		diff = in->buffer_used;
 		if (diff > size)
 			diff = size;
 
-		if (ostream_append(out, in->buffer + in->buffer_offset, diff))
+		if (ostream_append(out, in->buffer, diff))
 			return -1;
 
-		in->buffer_offset += diff;
+		in->buffer += diff;
+		in->buffer_used -= diff;
 		size -= diff;
 		total += diff;
 	}
diff --git a/lib/io/src/mem.c b/lib/io/src/mem.c
index d305a83..b1abbdb 100644
--- a/lib/io/src/mem.c
+++ b/lib/io/src/mem.c
@@ -10,6 +10,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 
 typedef struct {
 	istream_t base;
@@ -28,17 +29,16 @@ static int mem_in_precache(istream_t *strm)
 	mem_istream_t *mem = (mem_istream_t *)strm;
 	size_t diff;
 
-	if (strm->buffer_offset >= strm->buffer_used) {
-		strm->buffer_offset = 0;
-		strm->buffer_used = 0;
-	} else if (strm->buffer_offset > 0) {
-		memmove(strm->buffer,
-			strm->buffer + strm->buffer_offset,
-			strm->buffer_used - strm->buffer_offset);
+	assert(strm->buffer >= mem->buffer);
+	assert(strm->buffer <= (mem->buffer + mem->bufsz));
+	assert(strm->buffer_used <= mem->bufsz);
+	assert((size_t)(strm->buffer - mem->buffer) <=
+	       (mem->bufsz - strm->buffer_used));
 
-		strm->buffer_used -= strm->buffer_offset;
-		strm->buffer_offset = 0;
-	}
+	if (strm->buffer_used > 0)
+		memmove(mem->buffer, strm->buffer, strm->buffer_used);
+
+	strm->buffer = mem->buffer;
 
 	diff = mem->bufsz - strm->buffer_used;
 	if (diff > mem->size)
diff --git a/lib/io/src/unix/istream.c b/lib/io/src/unix/istream.c
index 24b18d6..db870d9 100644
--- a/lib/io/src/unix/istream.c
+++ b/lib/io/src/unix/istream.c
@@ -17,25 +17,21 @@ typedef struct {
 static int file_precache(istream_t *strm)
 {
 	file_istream_t *file = (file_istream_t *)strm;
-	ssize_t ret;
-	size_t diff;
-
-	if (strm->buffer_offset >= strm->buffer_used) {
-		strm->buffer_offset = 0;
-		strm->buffer_used = 0;
-	} else if (strm->buffer_offset > 0) {
-		memmove(strm->buffer,
-			strm->buffer + strm->buffer_offset,
-			strm->buffer_used - strm->buffer_offset);
-
-		strm->buffer_used -= strm->buffer_offset;
-		strm->buffer_offset = 0;
-	}
 
-	while (!strm->eof && strm->buffer_used < sizeof(file->buffer)) {
-		diff = sizeof(file->buffer) - strm->buffer_used;
+	assert(strm->buffer >= file->buffer);
+	assert(strm->buffer <= (file->buffer + BUFSZ));
+	assert(strm->buffer_used <= BUFSZ);
+	assert((size_t)(strm->buffer - file->buffer) <=
+	       (BUFSZ - strm->buffer_used));
+
+	if (strm->buffer_used > 0)
+		memmove(file->buffer, strm->buffer, strm->buffer_used);
+
+	strm->buffer = file->buffer;
 
-		ret = read(file->fd, strm->buffer + strm->buffer_used, diff);
+	while (!strm->eof && strm->buffer_used < BUFSZ) {
+		ssize_t ret = read(file->fd, file->buffer + strm->buffer_used,
+				   BUFSZ - strm->buffer_used);
 
 		if (ret == 0)
 			strm->eof = true;
diff --git a/lib/io/src/win32/istream.c b/lib/io/src/win32/istream.c
index 918b868..94c8584 100644
--- a/lib/io/src/win32/istream.c
+++ b/lib/io/src/win32/istream.c
@@ -23,27 +23,25 @@ static int file_precache(istream_t *strm)
 	DWORD diff, actual;
 	HANDLE hnd;
 
-	if (strm->buffer_offset >= strm->buffer_used) {
-		strm->buffer_offset = 0;
-		strm->buffer_used = 0;
-	} else if (strm->buffer_offset > 0) {
-		memmove(strm->buffer,
-			strm->buffer + strm->buffer_offset,
-			strm->buffer_used - strm->buffer_offset);
-
-		strm->buffer_used -= strm->buffer_offset;
-		strm->buffer_offset = 0;
-	}
-
 	if (strm->eof)
 		return 0;
 
+	assert(strm->buffer >= file->buffer);
+	assert(strm->buffer <= (file->buffer + BUFSZ));
+	assert(strm->buffer_used <= BUFSZ);
+	assert((size_t)(strm->buffer - file->buffer) <=
+	       (BUFSZ - strm->buffer_used));
+
+	if (strm->buffer_used > 0)
+		memmove(file->buffer, strm->buffer, strm->buffer_used);
+
+	strm->buffer = file->buffer;
 	hnd = file->path == NULL ? GetStdHandle(STD_INPUT_HANDLE) : file->hnd;
 
 	while (strm->buffer_used < sizeof(file->buffer)) {
 		diff = sizeof(file->buffer) - strm->buffer_used;
 
-		if (!ReadFile(hnd, strm->buffer + strm->buffer_used,
+		if (!ReadFile(hnd, file->buffer + strm->buffer_used,
 			      diff, &actual, NULL)) {
 			DWORD error = GetLastError();
 
diff --git a/lib/io/src/xfrm/istream.c b/lib/io/src/xfrm/istream.c
index b301209..152563f 100644
--- a/lib/io/src/xfrm/istream.c
+++ b/lib/io/src/xfrm/istream.c
@@ -20,28 +20,25 @@ static int xfrm_precache(istream_t *base)
 	istream_xfrm_t *xfrm = (istream_xfrm_t *)base;
 	int ret;
 
-	if (base->buffer_offset >= base->buffer_used) {
-		base->buffer_offset = 0;
-		base->buffer_used = 0;
-	} else if (base->buffer_offset > 0) {
-		memmove(base->buffer,
-			base->buffer + base->buffer_offset,
-			base->buffer_used - base->buffer_offset);
-
-		base->buffer_used -= base->buffer_offset;
-		base->buffer_offset = 0;
-	}
-
 	if (base->eof)
 		return 0;
 
+	assert(base->buffer >= xfrm->uncompressed);
+	assert(base->buffer <= (xfrm->uncompressed + BUFSZ));
+	assert(base->buffer_used <= BUFSZ);
+	assert((size_t)(base->buffer - xfrm->uncompressed) <=
+	       (BUFSZ - base->buffer_used));
+
+	if (base->buffer_used > 0)
+		memmove(xfrm->uncompressed, base->buffer, base->buffer_used);
+
+	base->buffer = xfrm->uncompressed;
+
 	ret = istream_precache(xfrm->wrapped);
 	if (ret != 0)
 		return ret;
 
 	for (;;) {
-		const sqfs_u32 in_sz = xfrm->wrapped->buffer_used;
-		const sqfs_u32 out_sz = sizeof(xfrm->uncompressed);
 		sqfs_u32 in_off = 0, out_off = base->buffer_used;
 		int mode = XFRM_STREAM_FLUSH_NONE;
 
@@ -49,9 +46,10 @@ static int xfrm_precache(istream_t *base)
 			mode = XFRM_STREAM_FLUSH_FULL;
 
 		ret = xfrm->xfrm->process_data(xfrm->xfrm,
-					       xfrm->wrapped->buffer, in_sz,
-					       base->buffer + out_off,
-					       out_sz - out_off,
+					       xfrm->wrapped->buffer,
+					       xfrm->wrapped->buffer_used,
+					       xfrm->uncompressed + out_off,
+					       BUFSZ - out_off,
 					       &in_off, &out_off, mode);
 
 		if (ret == XFRM_STREAM_ERROR) {
@@ -61,9 +59,10 @@ static int xfrm_precache(istream_t *base)
 		}
 
 		base->buffer_used = out_off;
-		xfrm->wrapped->buffer_offset = in_off;
+		xfrm->wrapped->buffer += in_off;
+		xfrm->wrapped->buffer_used -= in_off;
 
-		if (ret == XFRM_STREAM_BUFFER_FULL || out_off >= out_sz)
+		if (ret == XFRM_STREAM_BUFFER_FULL || out_off >= BUFSZ)
 			break;
 
 		ret = istream_precache(xfrm->wrapped);
diff --git a/lib/io/test/istream_read.c b/lib/io/test/istream_read.c
index 87e52c5..7029c38 100644
--- a/lib/io/test/istream_read.c
+++ b/lib/io/test/istream_read.c
@@ -101,7 +101,7 @@ int main(int argc, char **argv)
 	}
 
 	TEST_ASSERT(dummy->eof);
-	TEST_ASSERT(dummy->buffer_offset >= dummy->buffer_used);
+	TEST_ASSERT(dummy->buffer_used == 0);
 	sqfs_drop(dummy);
 	return EXIT_SUCCESS;
 }
diff --git a/lib/io/test/istream_skip.c b/lib/io/test/istream_skip.c
index 40d4ea4..c54a9cd 100644
--- a/lib/io/test/istream_skip.c
+++ b/lib/io/test/istream_skip.c
@@ -90,7 +90,7 @@ int main(int argc, char **argv)
 	}
 
 	TEST_ASSERT(dummy->eof);
-	TEST_ASSERT(dummy->buffer_offset >= dummy->buffer_used);
+	TEST_ASSERT(dummy->buffer_used == 0);
 	sqfs_drop(dummy);
 	return EXIT_SUCCESS;
 }
diff --git a/lib/io/test/stream_splice.c b/lib/io/test/stream_splice.c
index 9008d83..ab8a0e4 100644
--- a/lib/io/test/stream_splice.c
+++ b/lib/io/test/stream_splice.c
@@ -92,7 +92,7 @@ int main(int argc, char **argv)
 	}
 
 	TEST_ASSERT(in->eof);
-	TEST_ASSERT(in->buffer_offset >= in->buffer_used);
+	TEST_ASSERT(in->buffer_used == 0);
 	TEST_EQUAL_UI(total, end2);
 	TEST_EQUAL_UI(out_offset, end2);
 	sqfs_drop(in);
diff --git a/lib/io/test/xfrm.c b/lib/io/test/xfrm.c
index d06c558..ffb1f37 100644
--- a/lib/io/test/xfrm.c
+++ b/lib/io/test/xfrm.c
@@ -440,7 +440,6 @@ static void run_unpack_test(const void *blob, size_t size)
 	TEST_EQUAL_I(ret, 0);
 
 	TEST_EQUAL_UI(mem_istream->buffer_used, 0);
-	TEST_EQUAL_UI(mem_istream->buffer_offset, 0);
 	TEST_ASSERT(mem_istream->eof);
 
 	sqfs_drop(istream);
diff --git a/lib/tar/src/iterator.c b/lib/tar/src/iterator.c
index 532eb8c..b1be42d 100644
--- a/lib/tar/src/iterator.c
+++ b/lib/tar/src/iterator.c
@@ -71,10 +71,7 @@ static bool is_sparse_region(const tar_iterator_t *tar, sqfs_u64 *count)
 
 static int data_available(tar_iterator_t *tar, sqfs_u64 want, sqfs_u64 *out)
 {
-	sqfs_u64 avail = tar->stream->buffer_used - tar->stream->buffer_offset;
-
-	if ((want > avail) &&
-	    ((tar->stream->buffer_offset > 0) || avail == 0)) {
+	if (want > tar->stream->buffer_used) {
 		if (istream_precache(tar->stream)) {
 			tar->state = SQFS_ERROR_IO;
 			return -1;
@@ -84,11 +81,10 @@ static int data_available(tar_iterator_t *tar, sqfs_u64 want, sqfs_u64 *out)
 			tar->state = SQFS_ERROR_CORRUPTED;
 			return -1;
 		}
-
-		avail = tar->stream->buffer_used;
 	}
 
-	*out = avail <= want ? avail : want;
+	*out = tar->stream->buffer_used <= want ?
+		tar->stream->buffer_used : want;
 	return 0;
 }
 
@@ -104,43 +100,36 @@ static int strm_precache(istream_t *strm)
 	tar_istream_t *tar = (tar_istream_t *)strm;
 	sqfs_u64 diff;
 
-	strm->buffer_used -= strm->buffer_offset;
-	strm->buffer_offset = 0;
-
 	if (strm->eof)
-		return 0;
-
-	tar->parent->offset += tar->parent->last_chunk;
+		goto out_eof;
 
 	if (!tar->parent->last_sparse) {
-		tar->parent->stream->buffer_offset += tar->parent->last_chunk;
+		tar->parent->stream->buffer += tar->parent->last_chunk;
+		tar->parent->stream->buffer_used -= tar->parent->last_chunk;
 		tar->parent->record_size -= tar->parent->last_chunk;
 	}
 
+	tar->parent->offset += tar->parent->last_chunk;
 	if (tar->parent->offset >= tar->parent->file_size)
 		goto out_eof;
 
-	if (is_sparse_region(tar->parent, &diff)) {
+	tar->parent->last_sparse = is_sparse_region(tar->parent, &diff);
+
+	if (tar->parent->last_sparse) {
 		if (diff > sizeof(tar->buffer))
 			diff = sizeof(tar->buffer);
 
 		strm->buffer = tar->buffer;
-		strm->buffer_used = diff;
-		tar->parent->last_chunk = diff;
-		tar->parent->last_sparse = true;
-
 		memset(tar->buffer, 0, diff);
 	} else {
 		if (data_available(tar->parent, diff, &diff))
 			goto out_eof;
 
-		strm->buffer = tar->parent->stream->buffer +
-			tar->parent->stream->buffer_offset;
-		strm->buffer_used = diff;
-		tar->parent->last_chunk = diff;
-		tar->parent->last_sparse = false;
+		strm->buffer = tar->parent->stream->buffer;
 	}
 
+	strm->buffer_used = diff;
+	tar->parent->last_chunk = diff;
 	return 0;
 out_eof:
 	strm->eof = true;