59 lines
2.0 KiB
C
59 lines
2.0 KiB
C
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/* File : int2str.c
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Author : Richard A. O'Keefe
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Updated: 6 February 1993
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Defines: int2str()
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int2str(dst, radix, val)
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converts the (long) integer "val" to character form and moves it to
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the destination string "dst" followed by a terminating NUL. The
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result is normally a pointer to this NUL character, but if the radix
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is dud the result will be NullS and nothing will be changed.
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If radix is -2..-36, val is taken to be SIGNED.
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If radix is 2.. 36, val is taken to be UNSIGNED.
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That is, val is signed if and only if radix is. You will normally
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use radix -10 only through itoa and ltoa, for radix 2, 8, or 16
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unsigned is what you generally want.
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*/
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static char dig_vec[] =
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"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
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char *int2str(dst, radix, val)
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register char *dst;
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register int radix;
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register long val;
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{
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char buffer[65]; /* Ready for 64-bit machines */
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register char *p;
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if (radix < 2 || radix > 36) { /* Not 2..36 */
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if (radix > -2 || radix < -36) return (char *)0;
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if (val < 0) {
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*dst++ = '-';
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val = -val;
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}
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radix = -radix;
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}
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/* The slightly contorted code which follows is due to the
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fact that few machines directly support unsigned long / and %.
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Certainly the VAX C compiler generates a subroutine call. In
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the interests of efficiency (hollow laugh) I let this happen
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for the first digit only; after that "val" will be in range so
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that signed integer division will do. Sorry 'bout that.
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CHECK THE CODE PRODUCED BY YOUR C COMPILER. The first % and /
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should be unsigned, the second % and / signed, but C compilers
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tend to be extraordinarily sensitive to minor details of style.
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This works on a VAX, that's all I claim for it.
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*/
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p = &buffer[sizeof buffer];
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*--p = '\0';
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*--p = dig_vec[(unsigned long)val%(unsigned long)radix];
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val = (unsigned long)val/(unsigned long)radix;
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while (val != 0) *--p = dig_vec[val%radix], val /= radix;
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while (*dst++ = *p++) ;
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return dst-1;
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}
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