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129 lines
2.9 KiB
C
129 lines
2.9 KiB
C
#include <limits.h>
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#include <ctype.h>
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#include <errno.h>
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#include <stdlib.h>
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long __fastcall__ strtol (const char* nptr, char** endptr, int base)
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/* Convert a string to a long int */
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{
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register const char* S = nptr;
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unsigned long Val = 0;
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unsigned char Minus = 0;
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unsigned char Ovf = 0;
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unsigned CvtCount = 0;
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unsigned char DigitVal;
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unsigned long MaxVal;
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unsigned char MaxDigit;
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/* Skip white space */
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while (isspace (*S)) {
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++S;
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}
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/* Check for leading + or - sign */
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switch (*S) {
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case '-':
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Minus = 1;
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/* FALLTHROUGH */
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case '+':
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++S;
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}
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/* If base is zero, we may have a 0 or 0x prefix. If base is 16, we may
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* have a 0x prefix.
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*/
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if (base == 0) {
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if (*S == '0') {
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++S;
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if (*S == 'x' || *S == 'X') {
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++S;
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base = 16;
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} else {
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base = 8;
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}
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} else {
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base = 10;
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}
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} else if (base == 16 && *S == '0' && (S[1] == 'x' || S[1] == 'X')) {
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S += 2;
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}
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/* Determine the maximum valid number and (if the number is equal to this
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* value) the maximum valid digit.
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*/
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if (Minus) {
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MaxVal = LONG_MIN;
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} else {
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MaxVal = LONG_MAX;
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}
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MaxDigit = MaxVal % base;
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MaxVal /= base;
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/* Convert the number */
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while (1) {
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/* Convert the digit into a numeric value */
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if (isdigit (*S)) {
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DigitVal = *S - '0';
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} else if (isupper (*S)) {
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DigitVal = *S - ('A' - 10);
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} else if (islower (*S)) {
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DigitVal = *S - ('a' - 10);
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} else {
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/* Unknown character */
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break;
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}
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/* Don't accept a character that doesn't match base */
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if (DigitVal >= base) {
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break;
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}
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/* Don't accept anything that makes the final value invalid */
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if (Val > MaxVal || (Val == MaxVal && DigitVal > MaxDigit)) {
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Ovf = 1;
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}
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/* Calculate the next value if digit is not invalid */
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if (Ovf == 0) {
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Val = (Val * base) + DigitVal;
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++CvtCount;
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}
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/* Next character from input */
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++S;
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}
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/* Store the end pointer. If no conversion was performed, the value of
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* nptr is returned in endptr.
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*/
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if (endptr) {
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if (CvtCount > 0) {
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*endptr = (char*) S - 1;
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} else {
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*endptr = (char*) nptr;
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}
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}
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/* Handle overflow */
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if (Ovf) {
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errno = ERANGE;
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if (Minus) {
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return LONG_MIN;
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} else {
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return LONG_MAX;
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}
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}
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/* Return the result */
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if (Minus) {
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return -(long)Val;
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} else {
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return Val;
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}
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}
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