ref: c8e25d2a18c0395431abc5818a1d2f0561b0181f
dir: /sys/src/games/v8e/mem.c/
#include <u.h> #include <libc.h> #include "dat.h" #include "fns.h" static Segment * seglook(u32int a, int n, u32int **lp) { Segment *s; for(s = segs; s < segs + nelem(segs); s++) if(a >= s->start && a < s->start + s->size) break; if(s == segs + nelem(segs)) return nil; if(a + n > s->start + s->size) return nil; if(lp != nil) *lp = s->data + (a - s->start >> 2); return s; } u8int memread8(u32int a) { u32int *p; if(seglook(a, 1, &p) == nil) sysfatal("invalid read from %.8ux (pc=%.8ux)", a, curpc); switch(a & 3){ case 0: return *p; case 1: return *p >> 8; case 2: return *p >> 16; case 3: return *p >> 24; } return 0; } u16int memread16(u32int a) { u32int *p; if(seglook(a, 2, &p) == nil) sysfatal("invalid read from %.8ux (pc=%.8ux)", a, curpc); switch(a & 3){ case 0: return *p; case 1: return *p >> 8; case 2: return *p >> 16; case 3: return *p >> 24 | p[1] << 8; } return 0; } u32int memread32(u32int a) { u32int *p; if(seglook(a, 4, &p) == nil) sysfatal("invalid read from %.8ux (pc=%.8ux)", a, curpc); switch(a & 3){ case 0: return *p; case 1: return *p >> 8 | p[1] << 24; case 2: return *p >> 16 | p[1] << 16; case 3: return *p >> 24 | p[1] << 8; } return *p; } void memwrite(u32int a, u32int v, u32int m) { u32int *p; Segment *s; s = seglook(a, 4, &p); if(s == nil || (s->flags & SEGRO) != 0) sysfatal("invalid write to %.8ux=%.8ux (mask=%.8ux, pc=%.8ux)", a, v, m, curpc); *p = *p & ~m | v & m; }