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Track whether the current read stream supports seek(). For now, we

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assume yes unless seek has previously failed, but I fear I'll have to
avoid seeks under other circumstances.  (For instance, tape drives on
FreeBSD seem to return garbage from lseek().)  Also, optimize away
zero-byte skips.
This commit is contained in:
kientzle 2007-06-18 00:36:54 +00:00
parent 85dbbe2781
commit a5faebae4a
2 changed files with 22 additions and 0 deletions
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11
lib/libarchive/archive_read_open_fd.c
View File

@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
struct read_fd_data {
int fd;
size_t block_size;
char can_skip;
void *buffer;
};
@ -77,6 +78,7 @@ archive_read_open_fd(struct archive *a, int fd, size_t block_size)
return (ARCHIVE_FATAL);
}
mine->fd = fd;
mine->can_skip = 1;
return (archive_read_open2(a, mine, file_open, file_read, file_skip, file_close));
}
@ -121,8 +123,14 @@ file_skip(struct archive *a, void *client_data, off_t request)
struct read_fd_data *mine = (struct read_fd_data *)client_data;
off_t old_offset, new_offset;
if (!mine->can_skip)
return (0);
/* Reduce request to the next smallest multiple of block_size */
request = (request / mine->block_size) * mine->block_size;
if (request == 0)
return (0);
/*
* Hurray for lazy evaluation: if the first lseek fails, the second
* one will not be executed.
@ -130,6 +138,9 @@ file_skip(struct archive *a, void *client_data, off_t request)
if (((old_offset = lseek(mine->fd, 0, SEEK_CUR)) < 0) ||
((new_offset = lseek(mine->fd, request, SEEK_CUR)) < 0))
{
/* If seek failed once, it will probably fail again. */
mine->can_skip = 0;
if (errno == ESPIPE)
{
/*

11
lib/libarchive/archive_read_open_filename.c
View File

@ -52,6 +52,7 @@ struct read_file_data {
size_t block_size;
void *buffer;
mode_t st_mode; /* Mode bits for opened file. */
char can_skip; /* This file supports skipping. */
char filename[1]; /* Must be last! */
};
@ -95,6 +96,7 @@ archive_read_open_filename(struct archive *a, const char *filename,
mine->block_size = block_size;
mine->buffer = NULL;
mine->fd = -1;
mine->can_skip = 1;
return (archive_read_open2(a, mine, file_open, file_read, file_skip, file_close));
}
@ -165,8 +167,14 @@ file_skip(struct archive *a, void *client_data, off_t request)
struct read_file_data *mine = (struct read_file_data *)client_data;
off_t old_offset, new_offset;
if (!mine->can_skip) /* We can't skip, so ... */
return (0); /* ... skip zero bytes. */
/* Reduce request to the next smallest multiple of block_size */
request = (request / mine->block_size) * mine->block_size;
if (request == 0)
return (0);
/*
* Hurray for lazy evaluation: if the first lseek fails, the second
* one will not be executed.
@ -174,6 +182,9 @@ file_skip(struct archive *a, void *client_data, off_t request)
if (((old_offset = lseek(mine->fd, 0, SEEK_CUR)) < 0) ||
((new_offset = lseek(mine->fd, request, SEEK_CUR)) < 0))
{
/* If skip failed once, it will probably fail again. */
mine->can_skip = 0;
if (errno == ESPIPE)
{
/*