ref: 0f595fa896765dfdbe88c760ebd97edd8a1f123b
dir: /src/libscc/alloc.c/
#include <stdlib.h> #include <scc/scc.h> /* * This is the most pedantic piece of code that I have written * in my life. The next union is used to enforce the alignment * of the address returned by new(). A union has the alignment * of the field with the biggest alignment. This union has all * the types that we use in scc, and we round all the addresses * to the alignment of this struct, so we can be sure that any * pointer using that address will be safe. The field ap is * in the union to be sure that struct pointers are included * in the list, although they will have the same alignment or * smaller than void *, but I wanted to be pedantic. */ union hdr { union hdr *next; struct arena *ap; char c; unsigned char uc; int i; short s; long l; long long ll; float f; double d; long double ld; void *vp; }; struct arena { struct arena *next; union hdr *array; }; struct alloc { size_t size; size_t nmemb; size_t padding; struct arena *arena; union hdr *freep; }; static void newarena(Alloc *allocp) { struct arena *ap; union hdr *bp, *lim; size_t unit, n = allocp->nmemb; unit = (allocp->size-1) / sizeof(union hdr) + 1; ap = xmalloc(sizeof(struct arena)); ap->array = xmalloc(unit * sizeof(union hdr) * n); bp = ap->array; for (lim = &bp[unit * (n-1)]; bp < lim; bp += unit) bp->next = bp + unit; bp->next = NULL; ap->next = allocp->arena; allocp->arena = ap; allocp->freep = ap->array; } Alloc * alloc(size_t size, size_t nmemb) { Alloc *allocp = xmalloc(sizeof(*allocp)); allocp->size = size; allocp->nmemb = nmemb; allocp->arena = NULL; allocp->freep = NULL; return allocp; } void dealloc(Alloc *allocp) { struct arena *ap, *next; for (ap = allocp->arena; ap; ap = next) { next = ap->next; free(ap->array); free(ap); } free(allocp); } void * new(Alloc *allocp) { union hdr *bp; if (!allocp->freep) newarena(allocp); bp = allocp->freep; allocp->freep = bp->next; return bp; } void delete(Alloc *allocp, void *p) { union hdr *bp = p; bp->next = allocp->freep; allocp->freep = bp; }