libio: move istream buffer logic into interall callbacks

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

11 files changed, 222 insertions, 123 deletions

diff --git a/include/io/istream.h b/include/io/istream.h
index fca1440..8e86891 100644
--- a/include/io/istream.h
+++ b/include/io/istream.h
@@ -20,10 +20,10 @@
 typedef struct istream_t {
 	sqfs_object_t base;
 
-	size_t buffer_used;
-	const sqfs_u8 *buffer;
+	int (*get_buffered_data)(struct istream_t *strm, const sqfs_u8 **out,
+				 size_t *size, size_t want);
 
-	int (*precache)(struct istream_t *strm);
+	void (*advance_buffer)(struct istream_t *strm, size_t count);
 
 	const char *(*get_filename)(struct istream_t *strm);
 } istream_t;
@@ -121,17 +121,7 @@ SQFS_INLINE const char *istream_get_filename(istream_t *strm)
 SQFS_INLINE int istream_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
 					  size_t *size, size_t want)
 {
-	if (strm->buffer_used == 0 || strm->buffer_used < want) {
-		int ret = strm->precache(strm);
-		if (ret)
-			return ret;
-		if (strm->buffer_used == 0)
-			return 1;
-	}
-
-	*out = strm->buffer;
-	*size = strm->buffer_used;
-	return 0;
+	return strm->get_buffered_data(strm, out, size, want);
 }
 
 /**
@@ -148,8 +138,7 @@ SQFS_INLINE int istream_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
  */
 SQFS_INLINE void istream_advance_buffer(istream_t *strm, size_t count)
 {
-	strm->buffer += count;
-	strm->buffer_used -= count;
+	strm->advance_buffer(strm, count);
 }
 
 /**
diff --git a/lib/io/src/mem.c b/lib/io/src/mem.c
index 39e0d6b..bbb186a 100644
--- a/lib/io/src/mem.c
+++ b/lib/io/src/mem.c
@@ -20,38 +20,52 @@ typedef struct {
 
 	const void *data;
 	size_t size;
+	size_t offset;
+	size_t visible;
 
 	char *name;
 } mem_istream_t;
 
-static int mem_in_precache(istream_t *strm)
+static int mem_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
+				 size_t *size, size_t want)
 {
 	mem_istream_t *mem = (mem_istream_t *)strm;
-	size_t diff;
+	size_t have = mem->size - mem->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));
+	if (have > mem->bufsz)
+		have = mem->bufsz;
 
-	if (strm->buffer_used > 0)
-		memmove(mem->buffer, strm->buffer, strm->buffer_used);
+	if (want > have)
+		want = have;
 
-	strm->buffer = mem->buffer;
+	if (mem->visible == 0 || mem->visible < want) {
+		memcpy(mem->buffer + mem->visible,
+		       (const char *)mem->data + mem->offset + mem->visible,
+		       have - mem->visible);
+		mem->visible = have;
+	}
 
-	diff = mem->bufsz - strm->buffer_used;
-	if (diff > mem->size)
-		diff = mem->size;
+	*out = mem->buffer;
+	*size = mem->visible;
+	return (mem->visible == 0) ? 1 : 0;
+}
 
-	if (diff > 0) {
-		memcpy(mem->buffer + strm->buffer_used, mem->data, diff);
-		strm->buffer_used += diff;
-		mem->data = (const char *)mem->data + diff;
-		mem->size -= diff;
-	}
+static void mem_advance_buffer(istream_t *strm, size_t count)
+{
+	mem_istream_t *mem = (mem_istream_t *)strm;
 
-	return 0;
+	assert(count <= mem->visible);
+
+	if (count > 0 && count < mem->visible)
+		memmove(mem->buffer, mem->buffer + count, mem->visible - count);
+
+	mem->offset += count;
+	mem->visible -= count;
+
+	if (mem->visible < mem->bufsz) {
+		memset(mem->buffer + mem->visible, 0,
+		       mem->bufsz - mem->visible);
+	}
 }
 
 static const char *mem_in_get_filename(istream_t *strm)
@@ -88,8 +102,8 @@ istream_t *istream_memory_create(const char *name, size_t bufsz,
 	mem->data = data;
 	mem->size = size;
 	mem->bufsz = bufsz;
-	strm->buffer = mem->buffer;
-	strm->precache = mem_in_precache;
+	strm->get_buffered_data = mem_get_buffered_data;
+	strm->advance_buffer = mem_advance_buffer;
 	strm->get_filename = mem_in_get_filename;
 	return strm;
 }
diff --git a/lib/io/src/unix/istream.c b/lib/io/src/unix/istream.c
index 8a2dc26..60abff1 100644
--- a/lib/io/src/unix/istream.c
+++ b/lib/io/src/unix/istream.c
@@ -12,30 +12,35 @@ typedef struct {
 	int fd;
 
 	bool eof;
+	size_t buffer_offset;
+	size_t buffer_used;
 	sqfs_u8 buffer[BUFSZ];
 } file_istream_t;
 
-static int file_precache(istream_t *strm)
+static int precache(istream_t *strm)
 {
 	file_istream_t *file = (file_istream_t *)strm;
 
-	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 (file->eof)
+		return 0;
 
-	if (strm->buffer_used > 0)
-		memmove(file->buffer, strm->buffer, strm->buffer_used);
+	if (file->buffer_offset > 0 &&
+	    file->buffer_offset < file->buffer_used) {
+		memmove(file->buffer, file->buffer + file->buffer_offset,
+			file->buffer_used - file->buffer_offset);
+	}
 
-	strm->buffer = file->buffer;
+	file->buffer_used -= file->buffer_offset;
+	file->buffer_offset = 0;
 
-	while (!file->eof && strm->buffer_used < BUFSZ) {
-		ssize_t ret = read(file->fd, file->buffer + strm->buffer_used,
-				   BUFSZ - strm->buffer_used);
+	while (file->buffer_used < BUFSZ) {
+		ssize_t ret = read(file->fd, file->buffer + file->buffer_used,
+				   BUFSZ - file->buffer_used);
 
-		if (ret == 0)
+		if (ret == 0) {
 			file->eof = true;
+			break;
+		}
 
 		if (ret < 0) {
 			if (errno == EINTR)
@@ -45,12 +50,43 @@ static int file_precache(istream_t *strm)
 			return -1;
 		}
 
-		strm->buffer_used += ret;
+		file->buffer_used += ret;
 	}
 
 	return 0;
 }
 
+static int file_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
+				  size_t *size, size_t want)
+{
+	file_istream_t *file = (file_istream_t *)strm;
+
+	if (want > BUFSZ)
+		want = BUFSZ;
+
+	if (file->buffer_used == 0 ||
+	    (file->buffer_used - file->buffer_offset) < want) {
+		int ret = precache(strm);
+		if (ret)
+			return ret;
+	}
+
+	*out = file->buffer + file->buffer_offset;
+	*size = file->buffer_used - file->buffer_offset;
+	return (file->eof && *size == 0) ? 1 : 0;
+}
+
+static void file_advance_buffer(istream_t *strm, size_t count)
+{
+	file_istream_t *file = (file_istream_t *)strm;
+
+	assert(count <= file->buffer_used);
+
+	file->buffer_offset += count;
+
+	assert(file->buffer_offset <= file->buffer_used);
+}
+
 static const char *file_get_filename(istream_t *strm)
 {
 	file_istream_t *file = (file_istream_t *)strm;
@@ -93,8 +129,8 @@ istream_t *istream_open_file(const char *path)
 		goto fail_path;
 	}
 
-	strm->buffer = file->buffer;
-	strm->precache = file_precache;
+	strm->get_buffered_data = file_get_buffered_data;
+	strm->advance_buffer = file_advance_buffer;
 	strm->get_filename = file_get_filename;
 	return strm;
 fail_path:
@@ -119,8 +155,8 @@ istream_t *istream_open_stdin(void)
 		goto fail;
 
 	file->fd = STDIN_FILENO;
-	strm->buffer = file->buffer;
-	strm->precache = file_precache;
+	strm->get_buffered_data = file_get_buffered_data;
+	strm->advance_buffer = file_advance_buffer;
 	strm->get_filename = file_get_filename;
 	return strm;
 fail:
diff --git a/lib/io/src/win32/istream.c b/lib/io/src/win32/istream.c
index c4d7458..9bc32a0 100644
--- a/lib/io/src/win32/istream.c
+++ b/lib/io/src/win32/istream.c
@@ -15,10 +15,12 @@ typedef struct {
 	HANDLE hnd;
 
 	bool eof;
+	size_t buffer_offset;
+	size_t buffer_used;
 	sqfs_u8 buffer[BUFSZ];
 } file_istream_t;
 
-static int file_precache(istream_t *strm)
+static int precache(istream_t *strm)
 {
 	file_istream_t *file = (file_istream_t *)strm;
 	DWORD diff, actual;
@@ -27,22 +29,21 @@ static int file_precache(istream_t *strm)
 	if (file->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 (file->buffer_offset > 0 &&
+	    file->buffer_offset < file->buffer_used) {
+		memmove(file->buffer, file->buffer + file->buffer_offset,
+			file->buffer_used - file->buffer_offset);
+	}
 
-	if (strm->buffer_used > 0)
-		memmove(file->buffer, strm->buffer, strm->buffer_used);
+	file->buffer_used -= file->buffer_offset;
+	file->buffer_offset = 0;
 
-	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;
+	while (file->buffer_used < sizeof(file->buffer)) {
+		diff = sizeof(file->buffer) - file->buffer_used;
 
-		if (!ReadFile(hnd, file->buffer + strm->buffer_used,
+		if (!ReadFile(hnd, file->buffer + file->buffer_used,
 			      diff, &actual, NULL)) {
 			DWORD error = GetLastError();
 
@@ -63,12 +64,43 @@ static int file_precache(istream_t *strm)
 			break;
 		}
 
-		strm->buffer_used += actual;
+		file->buffer_used += actual;
 	}
 
 	return 0;
 }
 
+static int file_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
+				  size_t *size, size_t want)
+{
+	file_istream_t *file = (file_istream_t *)strm;
+
+	if (want > BUFSZ)
+		want = BUFSZ;
+
+	if (file->buffer_used == 0 ||
+	    (file->buffer_used - file->buffer_offset) < want) {
+		int ret = precache(strm);
+		if (ret)
+			return ret;
+	}
+
+	*out = file->buffer + file->buffer_offset;
+	*size = file->buffer_used - file->buffer_offset;
+	return (file->eof && *size == 0) ? 1 : 0;
+}
+
+static void file_advance_buffer(istream_t *strm, size_t count)
+{
+	file_istream_t *file = (file_istream_t *)strm;
+
+	assert(count <= file->buffer_used);
+
+	file->buffer_offset += count;
+
+	assert(file->buffer_offset <= file->buffer_used);
+}
+
 static const char *file_get_filename(istream_t *strm)
 {
 	file_istream_t *file = (file_istream_t *)strm;
@@ -122,7 +154,8 @@ istream_t *istream_open_file(const char *path)
 	free(wpath);
 
 	strm->buffer = file->buffer;
-	strm->precache = file_precache;
+	strm->get_buffered_data = file_get_buffered_data;
+	strm->advance_buffer = file_advance_buffer;
 	strm->get_filename = file_get_filename;
 	return strm;
 fail_path:
@@ -146,7 +179,8 @@ istream_t *istream_open_stdin(void)
 	sqfs_object_init(file, file_destroy, NULL);
 
 	strm->buffer = file->buffer;
-	strm->precache = file_precache;
+	strm->get_buffered_data = file_get_buffered_data;
+	strm->advance_buffer = file_advance_buffer;
 	strm->get_filename = file_get_filename;
 	return strm;
 }
diff --git a/lib/io/src/xfrm/istream.c b/lib/io/src/xfrm/istream.c
index bad3e22..c9bc41a 100644
--- a/lib/io/src/xfrm/istream.c
+++ b/lib/io/src/xfrm/istream.c
@@ -12,27 +12,28 @@ typedef struct istream_xfrm_t {
 	istream_t *wrapped;
 	xfrm_stream_t *xfrm;
 
+	size_t buffer_offset;
+	size_t buffer_used;
 	sqfs_u8 uncompressed[BUFSZ];
 } istream_xfrm_t;
 
-static int xfrm_precache(istream_t *base)
+static int precache(istream_t *base)
 {
 	istream_xfrm_t *xfrm = (istream_xfrm_t *)base;
 	int ret;
 
-	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);
+	if (xfrm->buffer_offset > 0 &&
+	    xfrm->buffer_offset < xfrm->buffer_used) {
+		memmove(xfrm->uncompressed,
+			xfrm->uncompressed + xfrm->buffer_offset,
+			xfrm->buffer_used - xfrm->buffer_offset);
+	}
 
-	base->buffer = xfrm->uncompressed;
+	xfrm->buffer_used -= xfrm->buffer_offset;
+	xfrm->buffer_offset = 0;
 
 	for (;;) {
-		sqfs_u32 in_off = 0, out_off = base->buffer_used;
+		sqfs_u32 in_off = 0, out_off = xfrm->buffer_used;
 		int mode = XFRM_STREAM_FLUSH_NONE;
 		const sqfs_u8 *ptr;
 		size_t avail;
@@ -41,10 +42,8 @@ static int xfrm_precache(istream_t *base)
 						sizeof(xfrm->uncompressed));
 		if (ret < 0)
 			return ret;
-		if (ret > 0) {
+		if (ret > 0)
 			mode = XFRM_STREAM_FLUSH_FULL;
-			avail = 0;
-		}
 
 		ret = xfrm->xfrm->process_data(xfrm->xfrm,
 					       ptr, avail,
@@ -58,7 +57,7 @@ static int xfrm_precache(istream_t *base)
 			return -1;
 		}
 
-		base->buffer_used = out_off;
+		xfrm->buffer_used = out_off;
 		istream_advance_buffer(xfrm->wrapped, in_off);
 
 		if (ret == XFRM_STREAM_BUFFER_FULL || out_off >= BUFSZ)
@@ -71,6 +70,37 @@ static int xfrm_precache(istream_t *base)
 	return 0;
 }
 
+static int xfrm_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
+				  size_t *size, size_t want)
+{
+	istream_xfrm_t *xfrm = (istream_xfrm_t *)strm;
+
+	if (want > BUFSZ)
+		want = BUFSZ;
+
+	if (xfrm->buffer_used == 0 ||
+	    (xfrm->buffer_used - xfrm->buffer_offset) < want) {
+		int ret = precache(strm);
+		if (ret)
+			return ret;
+	}
+
+	*out = xfrm->uncompressed + xfrm->buffer_offset;
+	*size = xfrm->buffer_used - xfrm->buffer_offset;
+	return (*size == 0) ? 1 : 0;
+}
+
+static void xfrm_advance_buffer(istream_t *strm, size_t count)
+{
+	istream_xfrm_t *xfrm = (istream_xfrm_t *)strm;
+
+	assert(count <= xfrm->buffer_used);
+
+	xfrm->buffer_offset += count;
+
+	assert(xfrm->buffer_offset <= xfrm->buffer_used);
+}
+
 static const char *xfrm_get_filename(istream_t *strm)
 {
 	istream_xfrm_t *xfrm = (istream_xfrm_t *)strm;
@@ -100,9 +130,9 @@ istream_t *istream_xfrm_create(istream_t *strm, xfrm_stream_t *xfrm)
 	stream->wrapped = sqfs_grab(strm);
 	stream->xfrm = sqfs_grab(xfrm);
 
-	base->precache = xfrm_precache;
+	base->get_buffered_data = xfrm_get_buffered_data;
+	base->advance_buffer = xfrm_advance_buffer;
 	base->get_filename = xfrm_get_filename;
-	base->buffer = stream->uncompressed;
 	return base;
 fail:
 	fprintf(stderr, "%s: error initializing decompressor stream.\n",
diff --git a/lib/io/test/istream_mem.c b/lib/io/test/istream_mem.c
index 84da9a9..a486899 100644
--- a/lib/io/test/istream_mem.c
+++ b/lib/io/test/istream_mem.c
@@ -63,8 +63,9 @@ int main(int argc, char **argv)
 			TEST_EQUAL_UI(ptr[j], byte_at_offset(i + j));
 		}
 
-		istream_advance_buffer(in, eat_all ? size : (size / 2));
+		diff = eat_all ? size : (size / 2);
 		eat_all = !eat_all;
+		istream_advance_buffer(in, diff);
 	}
 
 	sqfs_drop(in);
diff --git a/lib/io/test/istream_read.c b/lib/io/test/istream_read.c
index 176832b..8ba4540 100644
--- a/lib/io/test/istream_read.c
+++ b/lib/io/test/istream_read.c
@@ -100,7 +100,6 @@ int main(int argc, char **argv)
 		TEST_ASSERT(read_off <= end2);
 	}
 
-	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 15d7f5d..3a02c8c 100644
--- a/lib/io/test/istream_skip.c
+++ b/lib/io/test/istream_skip.c
@@ -89,7 +89,6 @@ int main(int argc, char **argv)
 		TEST_ASSERT(read_off <= end2);
 	}
 
-	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 223c39d..754f9cb 100644
--- a/lib/io/test/stream_splice.c
+++ b/lib/io/test/stream_splice.c
@@ -91,7 +91,6 @@ int main(int argc, char **argv)
 		TEST_EQUAL_UI(total, out_offset);
 	}
 
-	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 95b1f72..323987c 100644
--- a/lib/io/test/xfrm.c
+++ b/lib/io/test/xfrm.c
@@ -439,8 +439,6 @@ static void run_unpack_test(const void *blob, size_t size)
 	ret = istream_read(istream, &c, 1);
 	TEST_EQUAL_I(ret, 0);
 
-	TEST_EQUAL_UI(mem_istream->buffer_used, 0);
-
 	sqfs_drop(istream);
 	TEST_EQUAL_UI(((sqfs_object_t *)mem_istream)->refcount, 1);
 	TEST_EQUAL_UI(((sqfs_object_t *)xfrm)->refcount, 1);
diff --git a/lib/tar/src/iterator.c b/lib/tar/src/iterator.c
index df5c446..5d44c28 100644
--- a/lib/tar/src/iterator.c
+++ b/lib/tar/src/iterator.c
@@ -14,6 +14,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 #include <stdbool.h>
 
 typedef struct {
@@ -30,7 +31,6 @@ typedef struct {
 	sqfs_u64 offset;
 
 	size_t padding;
-	size_t last_chunk;
 	bool last_sparse;
 } tar_iterator_t;
 
@@ -86,8 +86,6 @@ static void drop_parent(tar_istream_t *tar, int state)
 			tar->parent->state = state;
 	}
 
-	((istream_t *)tar)->buffer_used = 0;
-	((istream_t *)tar)->buffer = tar->buffer;
 	tar->state = state;
 }
 
@@ -96,60 +94,63 @@ static const char *strm_get_filename(istream_t *strm)
 	return ((tar_istream_t *)strm)->parent->current.name;
 }
 
-static int strm_precache(istream_t *strm)
+static int strm_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
+				  size_t *size, size_t want)
 {
 	tar_istream_t *tar = (tar_istream_t *)strm;
 	sqfs_u64 diff;
+	int ret;
 
 	if (tar->parent == NULL)
 		return tar->state;
 
-	diff = (tar->parent->last_chunk - strm->buffer_used);
-	if (diff == 0 && strm->buffer_used > 0)
-		return tar->state;
-
-	if (!tar->parent->last_sparse) {
-		istream_advance_buffer(tar->parent->stream, diff);
-		tar->parent->record_size -= diff;
-	}
-
-	tar->parent->offset += diff;
 	if (tar->parent->offset >= tar->parent->file_size)
 		goto out_eof;
 
 	tar->parent->last_sparse = is_sparse_region(tar->parent, &diff);
 	if (diff == 0)
 		goto out_eof;
+	if (diff > want)
+		diff = want;
 
 	if (tar->parent->last_sparse) {
-		strm->buffer = tar->buffer;
-		strm->buffer_used = (diff <= sizeof(tar->buffer)) ?
+		*out = tar->buffer;
+		*size = (diff <= sizeof(tar->buffer)) ?
 			diff : sizeof(tar->buffer);
 	} else {
-		size_t avail;
-		int ret;
-
 		ret = istream_get_buffered_data(tar->parent->stream,
-						&strm->buffer, &avail, diff);
+						out, size, diff);
 		if (ret > 0)
 			goto fail_borked;
 		if (ret < 0)
 			goto fail_io;
-
-		strm->buffer_used = (diff <= avail) ? diff : avail;
+		if (*size > diff)
+			*size = diff;
 	}
 
-	tar->parent->last_chunk = strm->buffer_used;
-	return tar->state;
+	return 0;
 fail_io:
-	drop_parent(tar, SQFS_ERROR_IO);
+	drop_parent(tar, ret);
 	return tar->state;
 fail_borked:
 	drop_parent(tar, SQFS_ERROR_CORRUPTED);
 	return tar->state;
 out_eof:
 	drop_parent(tar, 0);
-	return tar->state;
+	tar->state = 1;
+	return 1;
+}
+
+static void strm_advance_buffer(istream_t *strm, size_t count)
+{
+	tar_istream_t *tar = (tar_istream_t *)strm;
+
+	if (!tar->parent->last_sparse) {
+		istream_advance_buffer(tar->parent->stream, count);
+		tar->parent->record_size -= count;
+	}
+
+	tar->parent->offset += count;
 }
 
 static void strm_destroy(sqfs_object_t *obj)
@@ -192,7 +193,6 @@ retry:
 		goto fail;
 
 	tar->offset = 0;
-	tar->last_chunk = 0;
 	tar->last_sparse = false;
 	tar->record_size = tar->current.record_size;
 	tar->file_size = tar->current.actual_size;
@@ -284,9 +284,9 @@ static int it_open_file_ro(dir_iterator_t *it, istream_t **out)
 	sqfs_object_init(strm, strm_destroy, NULL);
 	strm->parent = sqfs_grab(tar);
 
-	((istream_t *)strm)->precache = strm_precache;
+	((istream_t *)strm)->get_buffered_data = strm_get_buffered_data;
+	((istream_t *)strm)->advance_buffer = strm_advance_buffer;
 	((istream_t *)strm)->get_filename = strm_get_filename;
-	((istream_t *)strm)->buffer = strm->buffer;
 
 	tar->locked = true;
 	*out = (istream_t *)strm;