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runer112Matt Waltz
runer112
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Matt Waltz
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Improve and optimize random functions (#74)
Summary: * Add random and srandom, uint32_t variants of rand and srand. * random implements XSadd with shift parameters (19, 21, 8). This is a fast PRNG with a period of 2^128-1 which passes the dieharder tests (at least, no tests fail; some passes are weak). * rand, srand, and randInt use random as the underlying generator. * A complete random call takes 579 cycles. * A complete rand call takes 647 cycles. * A complete rand call previously took 4213 cycles and undoubtedly produced pseudorandom numbers of poorer quality. * Add random example and autotester configuration.
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‎examples/random/autotester.json

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{
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"rom": "84pce_515.rom",
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"transfer_files": [
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"bin/DEMO.8xp"
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],
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"target": {
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"name": "DEMO",
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"isASM": true
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},
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"sequence": [
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"action|launch",
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"hashWait|1",
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"key|enter",
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"hashWait|2"
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],
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"hashes": {
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"1": {
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"description": "VRAM filled with output of random()",
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"start": "vram_start",
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"size": "vram_16_size",
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"expected_CRCs": [ "5FB4A617" ]
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},
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"2": {
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"description": "Back to the home screen (exit check)",
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"start": "vram_start",
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"size": "vram_16_size",
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"expected_CRCs": [ "FFAF89BA", "101734A5", "9DA19F44" ]
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}
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}
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}

‎examples/random/makefile

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# ----------------------------
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# Set NAME to the program name
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# Set DEBUGMODE to "DEBUG" to use debug functions
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# Set ICON to the png icon file name
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# Set DESCRIPTION to display within a compatible shell
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# Set COMPRESSED to "YES" to create a compressed program
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# ** Add all shared library names to L **
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# ----------------------------
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NAME ?= DEMO
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DEBUGMODE ?= NDEBUG
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COMPRESSED ?= NO
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ICON ?= iconc.png
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DESCRIPTION ?= "C SDK Demo"
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L ?=
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# ----------------------------
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# Specify source and output locations
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# ----------------------------
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SRCDIR ?= src
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OBJDIR ?= obj
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BINDIR ?= bin
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GFXDIR ?= src/gfx
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# ----------------------------
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# Use OS helper functions (Advanced)
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# ----------------------------
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USE_FLASH_FUNCTIONS ?= YES
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include $(CEDEV)/include/.makefile

‎examples/random/readme.md

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### Random Fill Screen Demo
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This is a simple demo to demonstrate filling the screen with random colors.
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![Screenshot](screenshot.png)
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---
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This demo is a part of the C SDK Toolchain for use on the CE.

‎examples/random/screenshot.png

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‎examples/random/src/main.c

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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <tice.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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void main(void) {
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/* Fill VRAM with random data */
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uint32_t *lcd_Ram_i, *lcd_Ram_end = (uint32_t *) ((int) lcd_Ram + LCD_SIZE);
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for (lcd_Ram_i = (uint32_t *) lcd_Ram; lcd_Ram_i < lcd_Ram_end; lcd_Ram_i++) {
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*lcd_Ram_i = random();
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}
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/* Wait for a key press */
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while (!os_GetCSC());
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}

‎examples/random/test/expected.bin

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Binary file not shown.

‎src/ce/random.src

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.def _random
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.def __state
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.assume adl=1
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; uint32_t random(void);
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; https://github.com/MersenneTwister-Lab/XSadd/blob/master/xsadd.h#L75
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; using shift parameters (19, 21, 8) instead of (15, 18, 11)
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; uint32_t xsadd(uint32_t state[static 4])
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; {
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; uint32_t s0, s1, s2, t0, t1, t2, t3, z, result;
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; t0 = state[0];
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; state[0] = state[1]; state[1] = state[2]; state[2] = state[3];
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; s0 = t0 << 19;
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; t1 = t0 ^ s0;
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; s1 = t1 >> 21;
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; t2 = t1 ^ s1;
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; z = state[3];
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; s2 = z << 8;
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; t3 = t2 ^ s2;
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; state[3] = t3;
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; result = t3 + state[2];
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; return result;
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; }
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SEGMENT DATA
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__state:
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dl 0d0e0f10h,090a0b0ch,05060708h,01020304h
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SEGMENT CODE
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_random:
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; Read state[0] and perform state shifting.
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ld iy,__state ; iy = &state[0]
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ld hl,(iy+0*4+0) ; hl = hl(state[0])
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push hl
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ld hl,(iy+0*4+2) ; hl = eu(state[0])
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push hl
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lea hl,iy+1*4 ; hl = &state[1]
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lea de,iy+0*4 ; de = &state[0]
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ld bc,3*4
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ldir ; state[0] = state[1]
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; state[1] = state[2]
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; state[2] = state[3]
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pop bc
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pop de ; bcde = state[0] == t0
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;
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; s0 = t0 << 19 ==> s0h == 0 ==> t1h = t0h
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; s0l == 0 ==> t1l = t0l
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;
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; s1 = t1 >> 21 ==> s1e == 0 ==> t2e = t1e
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; s1u == 0 ==> t2u = t1u
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;
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; s2 = z << 8 ==> s2e == zu ==> t3e == t2e ^ s2e == t1e ^ s2e == t0e ^ s0e ^ s2e
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; s2u == zh ==> t3u == t2u ^ s2u == t1u ^ s2u == t0u ^ s0u ^ s2u
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; s2h == zl ==> t3h == t2h ^ s2h == t1h ^ s1h ^ s2h == t0h ^ s1h ^ s2h
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; s2l == 0 ==> t3l == t2l == t1l ^ s1l == t0l ^ s1l
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;
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; Calculate s0.
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ld h,d
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ld l,e ; hl = t0hl == t0 << 16
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add hl,hl
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add hl,hl
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add hl,hl ; hl = t0 << 19 = s0eu
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; h = s0e
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; l = s0u
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; Calculate t1e and t3e.
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ld a,b ; a = t0e
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xor a,h ; a = t0e ^ s0e == t1e
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ld h,a ; h = t1e
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xor a,(iy+3*4+2) ; a = t1e ^ zu == t2e ^ s2e == t3e
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ld (iy+3*4+3),a ; e(state[3]) = t3e
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ld b,a ; b = t3e
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; Calculate t1u and t3u.
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ld a,c ; a = t0u
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xor a,l ; a = t0u ^ s0u == t1u
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ld l,a ; l = t1u
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; hl = t1eu == t1 >> 16
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xor a,(iy+3*4+1) ; a = t1u ^ zh == t2u ^ s2u == t3u
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ld (iy+3*4+2),a ; u(state[3]) = t3u
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; Calculate s1.
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xor a,a ; a = 0
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add.s hl,hl
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adc a,a
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add.s hl,hl
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adc a,a
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add.s hl,hl
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adc a,a ; ahl = (t1 >> 16) << 3
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; ah = ((t1 >> 16) << 3) >> 8 == t1 >> 21 == s1hl
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; a = s1h
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; h = s1l
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; Calculate t3h.
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xor a,d ; a = s1h ^ t0h === s1h ^ t1h == t2h
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xor a,(iy+3*4+0) ; a = t2h ^ zl == t2h ^ s2h == t3h
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ld (iy+3*4+1),a ; h(state[3]) = t3h
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; Calculate t3l.
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ld a,e ; a = t0l == t1l
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xor a,h ; a = t1l ^ s1l == t2l == t3l
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ld (iy+3*4+0),a ; l(state[3]) = t3l
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; Calculate result.
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ld hl,(iy+3*4)
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ld a,b ; auhl = t3
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ld de,(iy+2*4)
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ld c,(iy+2*4+3) ; cude = state[2]
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add hl,de
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adc a,c ; auhl = t3 + state[2] = result
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ld e,a ; euhl = result
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ret

‎src/ce/srandom.src

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.ref __state
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.def _srandom
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.def __setstate
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.assume adl=1
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_MemClear equ 00210E0h
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; void srandom(uint32_t seed);
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_srandom:
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pop bc
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pop de
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ex (sp),hl ; lude = seed
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push de
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push bc
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ex de,hl
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ld a,e ; auhl = seed
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__setstate:
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ld (__state),hl
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ld hl,__state+3
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ld (hl),a
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ld b,12
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__setstateloop:
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inc hl
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ld (hl),b
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djnz __setstateloop
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ret

‎src/ce/tice.h

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*/
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/**
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* Creates a random integer value
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* Returns a pseudo-random 32-bit integer.
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*
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* @return the random integer
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*/
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uint32_t random(void);
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/**
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* Seeds the pseudo-random number generator used by random() and rand() with the
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* value seed.
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*
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* @param seed the seed value
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*/
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void srandom(uint32_t seed);
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/**
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* Returns a pseudo-random integer in the range of min to max-1.
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*/
2641
#define randInt(min, max) \
27-
((unsigned)rand() % ((max) - (min) + 1) + (min))
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((unsigned)random() % ((max) - (min) + 1) + (min))
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2944
/**
3045
* Delays for a number of milliseconds.

‎src/std/shared/rand.src

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1-
.ref __lmulu
2-
.ref __ladd
3-
.ref __lshru
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.ref __land
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.ref _random
52
.def _rand
6-
.def __next
73
.assume adl=1
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9-
; int rand(void);
104

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SEGMENT DATA
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__next:
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dl 1
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; int rand(void);
146

15-
SEGMENT CODE
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_rand:
17-
ld a,(__next+3)
18-
ld e,a
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ld a,65
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ld hl,(__next)
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ld bc,12996205
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call __lmulu
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ld bc,12345
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xor a,a
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call __ladd
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ld (__next),hl
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ld a,e
28-
ld (__next+3),a
29-
push hl
30-
pop bc
31-
ld l,16
32-
call __lshru
33-
ld e,a
34-
ld hl,bc
35-
ld bc,32767
36-
xor a,a
37-
jp __land
8+
call _random
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ld de,1<<23
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sbc hl,de
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ret p
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add hl,de
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ret

‎src/std/shared/srand.src

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.ref __next
2+
.ref __setstate
23
.def _srand
34
.assume adl=1
45

56
; void srand(unsigned int seed);
6-
7+
78
_srand:
8-
pop de
9-
pop hl
10-
push hl
11-
push de
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pop bc
10+
ex (sp),hl
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push bc
1212
xor a,a
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ld (__next),hl
14-
ld (__next+3),a
15-
ret
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jp __setstate

‎src/std/stdlib.h

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4949
extern double _huge_val;
5050
#define HUGE_VAL _huge_val /* overflow error */
5151

52-
#define RAND_MAX 32767 /* maximum value returned by rand() */
52+
#define RAND_MAX 8388607 /* maximum value returned by rand() */
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#ifndef SIZE_T_DEFINED
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#define SIZE_T_DEFINED

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