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/********************************* atoi_light.as *****************************
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* Author: Agner Fog
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* date created: 2018-03-23
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* Last modified: 2021-05-16
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* Version: 1.11
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* Project: ForwardCom library libc_light.li
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* Description: atoi: convert string to integer
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* This version is for CPUs with limited capabilities
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* C declaration: int64_t atoi(const char * str)
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*
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* Copyright 2018-2021 GNU General Public License http://www.gnu.org/licenses
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*****************************************************************************/
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code section execute align = 4 // code section
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_atoi function public reguse = 3, 0
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_atol function public reguse = 3, 0
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if (int64 r0 == 0) {jump EMPTYEND} // NULL pointer
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int64 sp -= 3*8 // save r2 - r4
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int64 [sp] = r2
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int64 [sp+8] = r3
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int64 [sp+0x10] = r4
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int r1 = 0 // state: 0: after whitespace
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// 1: after +/-
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// 2: after digit
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int64 r2 = 0 // value
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int r3 = 0 // sign
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int8 r4 = [r0] // read first character from string
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// loop through string until terminating zero
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while (int8+ r4 != 0) {
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if (uint8+ r4 <= ' ') { // whitespace
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if (int r1 != 0) {jump ERROREND} // space not allowed if state != 0. end of number
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jump NEXT // else
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}
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if (uint8+ r4 <= '-') { // '+' or '-'
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if (int r1 != 0) {jump ERROREND} // sign not allowed if state != 0. end of number
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int r1 = 1 // state = 1
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if (uint8+ r4 == '-') {
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int8+ r3 = 1 // sign
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jump NEXT // else
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}
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if (uint8+ r4 != '+') {
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jump ERROREND // anything else than '+'. end of number
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}
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}
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else {
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int8+ r4 -= '0' // subtract ASCII '0'
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if (uint8+ r4 > 9) {jump ERROREND} // anything else than 0-9. end of number
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//int64 r2 *= 10
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// multiply value by 10 without using mul instruction
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int64 r1 = r2 << 3 // value * 8
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int64 r2 <<= 1 // value * 2
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int64 r2 += r1 // value * 10
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int64 r2 += r4 // + digit
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int r1 = 2 // state = 2
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}
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NEXT:
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int64 r0++ // point to next character
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int8 r4 = [r0] // read next character from string
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}
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ERROREND: // jump here when a character that cannot be part of the string is met
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int64 r0 = r3 ? -r2 : r2 // change sign if r3
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int64 r2 = [sp] // restore r2 - r4
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int64 r3 = [sp+8]
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int64 r4 = [sp+0x10]
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int64 sp += 3*8
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EMPTYEND:
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return
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_atoi end
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code end
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