Given an object name, use open_istream() to get a git_istream handle
that you can read_istream() from as if you are using read(2) to read
the contents of the object, and close it with close_istream() when
you are done.
Currently, we do not do anything fancy--it just calls read_sha1_file()
and keeps the contents in memory as a whole, and carve it out as you
request with read_istream().
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
Makefile | 2 +
streaming.c | 196 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
streaming.h | 12 ++++
3 files changed, 210 insertions(+), 0 deletions(-)
create mode 100644 streaming.c
create mode 100644 streaming.h
diff --git a/Makefile b/Makefile
index 320ccc7..83bd539 100644
--- a/Makefile
+++ b/Makefile
@@ -552,6 +552,7 @@ LIB_H += sha1-lookup.h
LIB_H += sideband.h
LIB_H += sigchain.h
LIB_H += strbuf.h
+LIB_H += streaming.h
LIB_H += string-list.h
LIB_H += submodule.h
LIB_H += tag.h
@@ -657,6 +658,7 @@ LIB_OBJS += shallow.o
LIB_OBJS += sideband.o
LIB_OBJS += sigchain.o
LIB_OBJS += strbuf.o
+LIB_OBJS += streaming.o
LIB_OBJS += string-list.o
LIB_OBJS += submodule.o
LIB_OBJS += symlinks.o
diff --git a/streaming.c b/streaming.c
new file mode 100644
index 0000000..e03a374
--- /dev/null
+++ b/streaming.c
@@ -0,0 +1,196 @@
+#include "cache.h"
+#include "streaming.h"
+
+enum input_source {
+ stream_error = -1,
+ incore = 0,
+ loose = 1,
+ pack_non_delta = 2
+};
+
+typedef int (*open_istream_fn)(struct git_istream *,
+ struct object_info *, const unsigned char *,
+ enum object_type *, unsigned long *);
+typedef int (*close_istream_fn)(struct git_istream *);
+typedef ssize_t (*read_istream_fn)(struct git_istream *, char *, size_t);
+
+struct stream_vtbl {
+ close_istream_fn close;
+ read_istream_fn read;
+};
+
+#define open_method_decl(name) \
+ int open_istream_ ##name \
+ (struct git_istream *st, struct object_info *oi, \
+ const unsigned char *sha1, \
+ enum object_type *type, unsigned long *sz)
+
+#define close_method_decl(name) \
+ int close_istream_ ##name \
+ (struct git_istream *st)
+
+#define read_method_decl(name) \
+ ssize_t read_istream_ ##name \
+ (struct git_istream *st, char *buf, size_t sz)
+
+/* forward declaration */
+static open_method_decl(incore);
+static open_method_decl(loose);
+static open_method_decl(pack_non_delta);
+
+static open_istream_fn open_istream_tbl[] = {
+ open_istream_incore,
+ open_istream_loose,
+ open_istream_pack_non_delta,
+};
+
+struct git_istream {
+ enum input_source source;
+ const struct stream_vtbl *vtbl;
+ union {
+ struct {
+ char *buf; /* from read_object() */
+ unsigned long sz;
+ unsigned long read_ptr;
+ } incore;
+
+ struct {
+ int fd; /* open for reading */
+ /* NEEDSWORK: what else? */
+ } loose;
+
+ struct {
+ int fd; /* open for reading */
+ /* NEEDSWORK: what else? */
+ } in_pack;
+ } u;
+};
+
+int close_istream(struct git_istream *st)
+{
+ return st->vtbl->close(st);
+}
+
+ssize_t read_istream(struct git_istream *st, char *buf, size_t sz)
+{
+ return st->vtbl->read(st, buf, sz);
+}
+
+static enum input_source istream_source(const unsigned char *sha1,
+ enum object_type *type,
+ struct object_info *oi)
+{
+ unsigned long size;
+ int status;
+
+ oi->sizep = &size;
+ oi->want_deltainfo = 1;
+
+ status = sha1_object_info_extended(sha1, oi);
+ if (status < 0)
+ return stream_error;
+ *type = status;
+
+ switch (oi->whence) {
+ case OI_LOOSE:
+ return loose;
+ case OI_PACKED:
+ if (!oi->u.packed.delta && big_file_threshold <= size)
+ return pack_non_delta;
+ /* fallthru */
+ default:
+ return incore;
+ }
+}
+
+struct git_istream *open_istream(const unsigned char *sha1,
+ enum object_type *type,
+ unsigned long *sz)
+{
+ struct git_istream *st;
+ struct object_info oi;
+ const unsigned char *real = lookup_replace_object(sha1);
+ enum input_source src = istream_source(real, type, &oi);
+
+ if (src < 0)
+ return NULL;
+
+ st = xmalloc(sizeof(*st));
+ st->source = src;
+ if (open_istream_tbl[src](st, &oi, real, type, sz)) {
+ if (open_istream_incore(st, &oi, real, type, sz)) {
+ free(st);
+ st = NULL;
+ }
+ }
+ return st;
+}
+
+/*****************************************************************
+ *
+ * Loose object stream
+ *
+ *****************************************************************/
+
+static open_method_decl(loose)
+{
+ return -1; /* for now */
+}
+
+
+/*****************************************************************
+ *
+ * Non-delta packed object stream
+ *
+ *****************************************************************/
+
+static open_method_decl(pack_non_delta)
+{
+ return -1; /* for now */
+}
+
+
+/*****************************************************************
+ *
+ * In-core stream
+ *
+ *****************************************************************/
+
+static close_method_decl(incore)
+{
+ free(st->u.incore.buf);
+ return 0;
+}
+
+static read_method_decl(incore)
+{
+ size_t read_size = sz;
+ size_t remainder = st->u.incore.sz - st->u.incore.read_ptr;
+
+ if (remainder <= read_size)
+ read_size = remainder;
+ if (read_size) {
+ memcpy(buf, st->u.incore.buf + st->u.incore.read_ptr, read_size);
+ st->u.incore.read_ptr += read_size;
+ }
+ return read_size;
+}
+
+static struct stream_vtbl incore_vtbl = {
+ close_istream_incore,
+ read_istream_incore,
+};
+
+static open_method_decl(incore)
+{
+ st->u.incore.buf = read_sha1_file_extended(sha1, type, sz, 0);
+ st->u.incore.read_ptr = 0;
+ st->u.incore.sz = *sz;
+ st->vtbl = &incore_vtbl;
+
+ if (!st->u.incore.buf) {
+ free(st->u.incore.buf);
+ return -1;
+ }
+ return 0;
+}
diff --git a/streaming.h b/streaming.h
new file mode 100644
index 0000000..dff5e19
--- /dev/null
+++ b/streaming.h
@@ -0,0 +1,12 @@
+#ifndef STREAMING_H
+#define STREAMING_H 1
+#include "cache.h"
+
+/* opaque */
+struct git_istream;
+
+extern struct git_istream *open_istream(const unsigned char *, enum object_type *, unsigned long *);
+extern int close_istream(struct git_istream *);
+extern ssize_t read_istream(struct git_istream *, char *, size_t);
+
+#endif /* STREAMING_H */
--
1.7.5.1.365.g32b65
--
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