sergiotarxz/libvips
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get rid of a big stack allocation

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we were allocating 100kb in the C stack for a temporary string, instead
format directly to the destination area

some libc have very limited space on the C stack and can't afford this

see https://github.com/lovell/sharp/issues/242
This commit is contained in:
John Cupitt 2015-07-24 05:14:40 +01:00
parent c2e8406ca0
commit 96ed5eb684
1 changed files with 40 additions and 32 deletions
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72
libvips/iofuncs/buf.c
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@ -73,10 +73,6 @@
* ]| * ]|
*/ */
/* Largest string we can append in one operation.
*/
#define MAX_STRSIZE (100000)
/** /**
* VIPS_BUF_STATIC: * VIPS_BUF_STATIC:
* @TEXT: the storage area to use * @TEXT: the storage area to use
@ -320,7 +316,6 @@ vips_buf_appends( VipsBuf *buf, const char *str )
* *
* Returns: %FALSE on overflow, %TRUE otherwise. * Returns: %FALSE on overflow, %TRUE otherwise.
*/ */
gboolean gboolean
vips_buf_appendc( VipsBuf *buf, char ch ) vips_buf_appendc( VipsBuf *buf, char ch )
{ {
@ -342,7 +337,6 @@ vips_buf_appendc( VipsBuf *buf, char ch )
* *
* Returns: %FALSE on overflow, %TRUE otherwise. * Returns: %FALSE on overflow, %TRUE otherwise.
*/ */
gboolean gboolean
vips_buf_change( VipsBuf *buf, const char *old, const char *new ) vips_buf_change( VipsBuf *buf, const char *old, const char *new )
{ {
@ -399,29 +393,6 @@ vips_buf_removec( VipsBuf *buf, char ch )
return( TRUE ); return( TRUE );
} }
/**
* vips_buf_appendf:
* @buf: the buffer
* @fmt: <function>printf()</function>-style format string
* @...: arguments to format string
*
* Format the string and append to @buf.
*
* Returns: %FALSE on overflow, %TRUE otherwise.
*/
gboolean
vips_buf_appendf( VipsBuf *buf, const char *fmt, ... )
{
char str[MAX_STRSIZE];
va_list ap;
va_start( ap, fmt );
(void) vips_vsnprintf( str, MAX_STRSIZE, fmt, ap );
va_end( ap );
return( vips_buf_appends( buf, str ) );
}
/** /**
* vips_buf_vappendf: * vips_buf_vappendf:
* @buf: the buffer * @buf: the buffer
@ -435,11 +406,48 @@ vips_buf_appendf( VipsBuf *buf, const char *fmt, ... )
gboolean gboolean
vips_buf_vappendf( VipsBuf *buf, const char *fmt, va_list ap ) vips_buf_vappendf( VipsBuf *buf, const char *fmt, va_list ap )
{ {
char str[MAX_STRSIZE]; int avail;
char *p;
(void) vips_vsnprintf( str, MAX_STRSIZE, fmt, ap ); if( buf->full )
return( FALSE );
return( vips_buf_appends( buf, str ) ); avail = buf->mx - buf->i - 4;
p = buf->base + buf->i;
(void) vips_vsnprintf( p, avail, fmt, ap );
buf->i += strlen( p );
if( buf->i >= buf->mx - 4 ) {
buf->full = TRUE;
strcpy( buf->base + buf->mx - 4, "..." );
buf->i = buf->mx - 1;
return( FALSE );
}
return( TRUE );
}
/**
* vips_buf_appendf:
* @buf: the buffer
* @fmt: <function>printf()</function>-style format string
* @...: arguments to format string
*
* Format the string and append to @buf.
*
* Returns: %FALSE on overflow, %TRUE otherwise.
*/
gboolean
vips_buf_appendf( VipsBuf *buf, const char *fmt, ... )
{
va_list ap;
gboolean result;
va_start( ap, fmt );
result = vips_buf_vappendf( buf, fmt, ap );
va_end( ap );
return( result );
} }
/** /**