66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
#include <string.h>
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#include <libowfat/str.h>
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#include <libowfat/uint32.h>
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#include "bstr.h"
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int bstr_diff2(const char* a,const char* b,size_t blen) {
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const char* A,* B;
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int j;
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/* like str_diff, just for bstrs */
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if (*a)
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A=a+str_len(a);
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else {
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A=a+5+uint32_read(a+1);
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a+=5;
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}
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// If adding blen to b would overflow, reduce blen.
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// The comparison can never get that far because the end of the
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// address space is reserved for the kernel. Make sure to revisit this
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// if you want to use this function in kernel space.
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uintptr_t c = ~(uintptr_t)b;
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if (blen > c) blen = c;
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B=b+blen;
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for (;;) {
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if (a==A) {
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if (b==B)
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return 0;
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else
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return -1;
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} else
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if (b==B)
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return 1;
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if ((j=((unsigned char)*a-(unsigned char)*b))) break;
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++a; ++b;
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}
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return j;
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}
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#ifdef UNITTEST
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#include <assert.h>
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int main() {
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assert(bstr_diff2("bar","foo",3) < 0);
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assert(bstr_diff2("foo","bar",3) > 0);
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assert(bstr_diff2("foo1","foo",3) > 0);
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assert(bstr_diff2("foo","foo1",4) < 0);
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assert(bstr_diff2("foo","foo",3) == 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""bar","foo",3) < 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""foo","bar",3) > 0);
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assert(bstr_diff2("\x00\x04\x00\x00\x00""foo1","foo",3) > 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""foo","foo1",4) < 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""foo","foo",3) == 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""bar","foo",3) < 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""foo","bar",3) > 0);
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assert(bstr_diff2("\x00\x04\x00\x00\x00""foo1","foo",3) > 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""foo","foo1",4) < 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""foo","foo",3) == 0);
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assert(bstr_diff2("\x00\x05\x00\x00\x00""f\x00ord","fnord",5) < 0);
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assert(bstr_diff2("\x00\x05\x00\x00\x00""f\x00ord","f\x00ort",5) < 0);
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assert(bstr_diff2("\x00\x03\x00\x00\x00""f\xf6o","foo",3) > 0);
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}
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#endif
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