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93 lines
3.9 KiB
C
93 lines
3.9 KiB
C
#ifndef RANGECHECK_H
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#define RANGECHECK_H
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#include <inttypes.h>
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#include <stddef.h>
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/* return 0 for range error / overflow, 1 for ok */
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#if defined(__GNUC__) && defined(__OPTIMIZE__)
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#define __static extern
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#else
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#define __static static
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#endif
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/* does ptr point to one of buf[0], buf[1], ... buf[len-1]? */
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__static inline int range_ptrinbuf(const void* buf,size_t len,const void* ptr) {
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register const char* c=(const char*)buf; /* no pointer arithmetic on void* */
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return (c && /* is buf non-NULL? */
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((uintptr_t)c)+len>(uintptr_t)c && /* gcc 4.1 miscompiles without (uintptr_t) */
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/* catch integer overflows and fail if buffer is 0 bytes long */
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/* because then ptr can't point _in_ the buffer */
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(uintptr_t)((const char*)ptr-c)<len); /* this one is a little tricky.
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"ptr-c" checks the offset of ptr in the buffer is inside the buffer size.
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Now, ptr-c can underflow; say it is -1. When we cast it to uintptr_t, it becomes
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a very large number. */
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}
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/* Is this a plausible buffer?
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* Check whether buf is NULL, and whether buf+len overflows.
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* Does NOT check whether buf has a non-zero length! */
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__static inline int range_validbuf(const void* buf,size_t len) {
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return (buf && (uintptr_t)buf+len>=(uintptr_t)buf);
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}
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/* is buf2[0..len2-1] inside buf1[0..len-1]? */
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__static inline int range_bufinbuf(const void* buf1,size_t len1,const void* buf2,size_t len2) {
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return range_validbuf(buf1,len1) &&
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range_validbuf(buf2,len2) &&
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buf1<=buf2 &&
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(ptrdiff_t)buf1+len1>=(ptrdiff_t)buf2+len2;
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}
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/* does an array of "elements" members of size "membersize" starting at
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* "arraystart" lie inside buf1[0..len-1]? */
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int range_arrayinbuf(const void* buf,size_t len,
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const void* arraystart,size_t elements,size_t membersize);
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/* does an ASCIIZ string starting at "ptr" lie in buf[0..len-1]? */
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int range_strinbuf(const void* buf,size_t len,const void* stringstart);
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/* does an UTF-16 string starting at "ptr" lie in buf[0..len-1]? */
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int range_str2inbuf(const void* buf,size_t len,const void* stringstart);
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/* does an UTF-32 string starting at "ptr" lie in buf[0..len-1]? */
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int range_str4inbuf(const void* buf,size_t len,const void* stringstart);
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/* I originally omitted addition and substraction because it appeared
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* trivial. You could just add the two numbers and see if it was
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* smaller than either of them. This always worked for me because I
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* only cared about unsigned arithmetic, but for signed arithmetic,
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* adding two numbers is undefined if the result does not fit in the
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* int. gcc has started to actually use this undefinedness to screw
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* you. The following code illustrates this:
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* int a=INT_MAX,b=a+5;
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* if (b<a) abort(); // whole statement optimized away by gcc 4.1
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* // at this point, b<a
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* So I decided to add some integer overflow protection functionality
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* here for addition and subtraction, too. */
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/* first, we need a type independent way to find the min and max values
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* for each type, so the macros also work for integer types you defined
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* yourself */
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#define __MIN_UNSIGNED(type) ((type)0)
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#define __MIN_SIGNED(type) (((type)-1)<<(sizeof(type)*8-1))
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/* we use <1 and not <0 to avoid a gcc warning */
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#define __MIN(type) ((type)-1 < 1?__MIN_SIGNED(type):__MIN_UNSIGNED(type))
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#define __MAX(type) ((type)~__MIN(type))
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#define assign(dest,src) ({ typeof(src) __x=(src); typeof(dest) __y=__x; (__x==__y && ((__x<1) == (__y<1))?(void)((dest)=__y),0:1); })
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/* if a+b is defined and does not have an integer overflow, do c=a+b and
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* return 0. Otherwise, return 1. */
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#define add_of(c,a,b) ({ typeof(a) __a=a; typeof(b) __b=b; (__b)<1?((__MIN(typeof(c))-(__b)<=(__a))?assign(c,__a+__b):1) : ((__MAX(typeof(c))-(__b)>=(__a))?assign(c,__a+__b):1); })
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#define sub_of(c,a,b) ({ typeof(a) __a=a; typeof(b) __b=b; (__b)<1?((__MAX(typeof(c))-(__b)>=(__a))?assign(c,__a-__b):1) : ((__MIN(typeof(c))+(__b)<=(__a))?assign(c,__a-__b):1); })
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#undef __static
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#endif
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