[Patch v5 3/6] util: add gz_readline
Austin Clements
amdragon at MIT.EDU
Tue Apr 1 20:26:44 PDT 2014
Quoth David Bremner on Apr 01 at 10:16 pm:
> The idea is to provide a more or less drop in replacement for readline
> to read from zlib/gzip streams. Take the opportunity to replace
> malloc with talloc.
> ---
> util/Makefile.local | 2 +-
> util/util.h | 12 +++++++++
> util/zlib-extra.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> util/zlib-extra.h | 11 ++++++++
> 4 files changed, 100 insertions(+), 1 deletion(-)
> create mode 100644 util/util.h
> create mode 100644 util/zlib-extra.c
> create mode 100644 util/zlib-extra.h
>
> diff --git a/util/Makefile.local b/util/Makefile.local
> index 29c0ce6..e2a5b65 100644
> --- a/util/Makefile.local
> +++ b/util/Makefile.local
> @@ -4,7 +4,7 @@ dir := util
> extra_cflags += -I$(srcdir)/$(dir)
>
> libutil_c_srcs := $(dir)/xutil.c $(dir)/error_util.c $(dir)/hex-escape.c \
> - $(dir)/string-util.c $(dir)/talloc-extra.c
> + $(dir)/string-util.c $(dir)/talloc-extra.c $(dir)/zlib-extra.c
>
> libutil_modules := $(libutil_c_srcs:.c=.o)
>
> diff --git a/util/util.h b/util/util.h
> new file mode 100644
> index 0000000..8663cfc
> --- /dev/null
> +++ b/util/util.h
> @@ -0,0 +1,12 @@
> +#ifndef _UTIL_H
> +#define _UTIL_H
> +
> +typedef enum util_status {
> + UTIL_SUCCESS = 0,
> + UTIL_ERROR = 1,
> + UTIL_OUT_OF_MEMORY,
> + UTIL_EOF,
> + UTIL_FILE,
> +} util_status_t;
> +
> +#endif
> diff --git a/util/zlib-extra.c b/util/zlib-extra.c
> new file mode 100644
> index 0000000..cb1eba0
> --- /dev/null
> +++ b/util/zlib-extra.c
> @@ -0,0 +1,76 @@
> +/* zlib-extra.c - Extra or enhanced routines for compressed I/O.
> + *
> + * Copyright (c) 2014 David Bremner
> + *
> + * This program is free software: you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation, either version 3 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see http://www.gnu.org/licenses/ .
> + *
> + * Author: David Bremner <david at tethera.net>
> + */
> +
> +#include "zlib-extra.h"
> +#include <talloc.h>
> +#include <stdio.h>
> +#include <string.h>
> +
> +/* mimic POSIX/glibc getline, but on a zlib gzFile stream, and using talloc */
> +util_status_t
> +gz_getline (void *talloc_ctx, char **bufptr, size_t *bufsiz, ssize_t *bytes_read,
Talloc chunks know their size, so rather than taking bufsize, use
talloc_get_size (or talloc_array_length if you switch to talloc array
functions below).
> + gzFile stream)
> +{
> + size_t len = *bufsiz;
> + char *buf = *bufptr;
> + size_t offset = 0;
> +
> + if (len == 0 || buf == NULL) {
> + /* same as getdelim from gnulib */
> + len = 120;
This is presumably because glibc's malloc has an 8 byte header. Fun
fact: talloc has a 104 byte header (on 64-bit and including the malloc
header).
> + buf = talloc_size (talloc_ctx, len);
> + if (buf == NULL)
> + return UTIL_OUT_OF_MEMORY;
> + }
> +
> + while (1) {
> + if (! gzgets (stream, buf + offset, len - offset)) {
> + int zlib_status = 0;
> + (void) gzerror (stream, &zlib_status);
> + switch (zlib_status) {
> + case Z_OK:
> + /* follow getline behaviour */
> + *bytes_read = -1;
Is this really what getline does when the last line of a file isn't
\n-terminated?
> + return UTIL_EOF;
> + break;
> + case Z_ERRNO:
> + return UTIL_FILE;
> + break;
> + default:
> + return UTIL_ERROR;
> + }
> + }
> +
> + offset += strlen (buf + offset);
> +
> + if ( buf[offset - 1] == '\n' )
Too many spaces!
> + break;
> +
> + len *= 2;
> + buf = talloc_realloc (talloc_ctx, buf, char, len);
Or talloc_realloc_size, to match the initial talloc_size.
Alternatively, the initial talloc_size could be a talloc_array.
> + if (buf == NULL)
> + return UTIL_OUT_OF_MEMORY;
> + }
> +
> + *bufptr = buf;
> + *bufsiz = len;
> + *bytes_read = offset;
> + return UTIL_SUCCESS;
> +}
> diff --git a/util/zlib-extra.h b/util/zlib-extra.h
> new file mode 100644
> index 0000000..ed46ac1
> --- /dev/null
> +++ b/util/zlib-extra.h
> @@ -0,0 +1,11 @@
> +#ifndef _ZLIB_EXTRA_H
> +#define _ZLIB_EXTRA_H
> +
> +#include <zlib.h>
> +#include "util.h"
I'd put "util.h" first so we're more likely to catch missing header
dependencies (obviously util.h doesn't have any right now, but in the
future).
Also, I'd put a blank line after the #includes.
> +/* Like getline, but read from a gzFile. Allocation is with talloc */
> +util_status_t
> +gz_getline (void *ctx, char **lineptr, size_t *line_size, ssize_t *bytes_read,
> + gzFile stream);
> +
> +#endif
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