Am 19.05.2011 23:33, schrieb Junio C Hamano:
> 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 | 199 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> streaming.h | 15 +++++
> 3 files changed, 216 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..84330b4
> --- /dev/null
> +++ b/streaming.c
> @@ -0,0 +1,199 @@
> +/*
> + * Copyright (c) 2011, Google Inc.
> + */
> +#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 *);
> +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)
> +
> +#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)
It would be nice if those macros could be got rid of once the interface
stabilizes.
> +
> +/* 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,
> +};
These three uses of the macro can be avoided by moving open_istream_tbl
and open_istream() to the end of the file. It would be just as clear
and clean, albeit not as close to literal programming style.
> +
> +struct git_istream {
> + enum input_source source;
source seems to be write-only.
> + const struct stream_vtbl *vtbl;
> + unsigned long size; /* inflated size of full object */
> +
> + union {
> + struct {
> + char *buf; /* from read_object() */
> + 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;
> + 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.is_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 *size)
> +{
> + 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)) {
> + if (open_istream_incore(st, &oi, real, type)) {
> + free(st);
> + st = NULL;
return NULL;
// Otherwise we get a problem three lines down.
> + }
> + }
> + *size = st->size;
> + 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->size - 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, &st->size, 0);
> + st->u.incore.read_ptr = 0;
> + st->vtbl = &incore_vtbl;
> +
> + if (!st->u.incore.buf) {
> + free(st->u.incore.buf);
free(NULL) is a noop.
> + return -1;
> + }
> + return 0;
> +}
> diff --git a/streaming.h b/streaming.h
> new file mode 100644
> index 0000000..18cbe68
> --- /dev/null
> +++ b/streaming.h
> @@ -0,0 +1,15 @@
> +/*
> + * Copyright (c) 2011, Google Inc.
> + */
> +#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 */
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