Date: Tue, 1 Apr 2014 23:26:44 -0400
From: Austin Clements <amdragon@MIT.EDU>
To: David Bremner <david@tethera.net>
Subject: Re: [Patch v5 3/6] util: add gz_readline
Message-ID: <20140402032644.GB25677@mit.edu>
References: <1396401381-18128-1-git-send-email-david@tethera.net>
	<1396401381-18128-4-git-send-email-david@tethera.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1396401381-18128-4-git-send-email-david@tethera.net>
User-Agent: Mutt/1.5.21 (2010-09-15)
Cc: notmuch@notmuchmail.org
Precedence: list

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@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