Re: [Libvir] PATCH: Make the virBuffer API harder to misuse

The following set of changes adjust the way errors are handled in the virBuffer routines. The key idea is to make it hard (impossible) to misuse the API, with each change addressing one of the errors scenarios I've found in existing code using the routines.

- The contents of the struct are no longer public. Rationale: This stops people accessing the buffer directly, thus preventing use of data which may be in an error state.

Index: src/buf.h =================================================================== RCS file: /data/cvs/libvirt/src/buf.h,v retrieving revision 1.5 diff -u -p -r1.5 buf.h --- src/buf.h 20 Feb 2008 15:29:13 -0000 1.5 +++ src/buf.h 26 Apr 2008 16:24:38 -0000 @@ -20,22 +20,45 @@ */ typedef struct _virBuffer virBuffer; typedef virBuffer *virBufferPtr; + +#ifndef __VIR_BUFFER_C__ +/* This constant must match size of the actual struct + in the buf.c file */ +#if __WORDSIZE == 64 +#define __SIZEOF_VIR_BUFFER 32 +#define VIR_BUFFER_INITIALIZER { { 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0 \ + } } +#else +#define __SIZEOF_VIR_BUFFER 16 +#define VIR_BUFFER_INITIALIZER { { 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0, \ + 0, 0, 0, 0 \ + } } +#endif struct _virBuffer { - char *content; /* The buffer content UTF8 */ - unsigned int use; /* The buffer size used */ - unsigned int size; /* The buffer size */ + char *padding[__SIZEOF_VIR_BUFFER]; /* This struct contents is private */ };