ref: 063145fc84acfe092a75d7bd2206987c147aa2b3
dir: /lib/std/alloc.myr/
use "die" use "extremum" use "memops" use "syswrap" use "threadhooks" use "types" use "units" use "bytealloc" use "backtrace" use "memops" /* The allocator implementation here is based on Bonwick's slab allocator. For small allocations (up to Bktmax), it works by requesting large, power of two aligned chunks from the operating system, and breaking them into a linked list of equal sized chunks. Allocations are then satisfied by taking the head of the list of chunks. Empty slabs are removed from the freelist. The data structure looks something like this: Bkts: [16 byte] -> [slab hdr | chunk -> chunk -> chunk] -> [slab hdr | chunk -> chunk -> chunk] [32 byte] -> Zslab [64 byte] -> [slab hdr | chunk -> chunk] ... [32k byte] -> ... Large allocations are simply satisfied by mmap(). */ pkg std = generic alloc : ( -> @a#) generic zalloc : ( -> @a#) generic free : (v:@a# -> void) generic slalloc : (len : size -> @a[:]) generic slzalloc : (len : size -> @a[:]) generic slgrow : (sl : @a[:]#, len : size -> @a[:]) generic slzgrow : (sl : @a[:]#, len : size -> @a[:]) generic slfree : (sl : @a[:] -> void) ;; type slheader = struct cap : size /* capacity in bytes */ magic : size /* magic check value */ ;; /* Allocates an object of type @a, returning a pointer to it. */ generic alloc = {-> @a# -> (bytealloc(sizeof(@a)) : @a#) } generic zalloc = {-> @a# -> (zbytealloc(sizeof(@a)) : @a#) } /* Frees a value of type @a */ generic free = {v:@a# -> void bytefree((v : byte#), sizeof(@a)) } /* allocates a slice of 'len' elements. */ generic slalloc = {len var p, sz if len == 0 -> [][:] ;; sz = len*sizeof(@a) + align(sizeof(slheader), Align) sz = allocsz(sz) p = bytealloc(sz + sizeof(size)) p = inithdr(p, sz) -> (p : @a#)[0:len] } generic slzalloc = {len var p, sz if len == 0 -> [][:] ;; sz = len*sizeof(@a) + align(sizeof(slheader), Align) sz = allocsz(sz) p = zbytealloc(sz + sizeof(size)) p = inithdr(p, sz) -> (p : @a#)[0:len] } const inithdr = {p, sz var phdr, pdat, pend phdr = (p : slheader#) phdr.cap = sz - align(sizeof(slheader), Align) /* add start/end magics */ phdr.magic = (0xdeadbeefbadf00d : size) pdat = (p : size) + align(sizeof(slheader), Align) pend = ((pdat : size) + sz - align(sizeof(slheader), Align) : size#) pend# = 0xfee1deadfee1dead -> (pdat : byte#) } const checkhdr = {p var phdr, pend, addr addr = (p : size) addr -= align(sizeof(slheader), Align) /* check start/end magics */ phdr = (addr : slheader#) iassert(phdr.magic == (0xdeadbeefbadf00d : size), "corrupt memory\n") pend = ((p : size) + phdr.cap : size#) iassert(pend# == 0xfee1deadfee1dead, "corrupt memory") } /* Frees a slice */ generic slfree = {sl var head, sz if (sl : byte#) == Zslicep -> void ;; checkhdr((sl : byte#)) head = ((sl : byte#) : size) head -= align(sizeof(slheader), Align) sz = slcap((sl : byte#)) + align(sizeof(slheader), Align) bytefree((head : byte#), sz + sizeof(size)) } /* Grows a slice */ generic slgrow = {sl : @a[:]#, len var cap, nel var new var n /* if the slice doesn't need a bigger bucket, we don't need to realloc. */ cap = 0 if (sl# : byte#) != Zslicep cap = slcap((sl# : byte#)) ;; if cap >= len*sizeof(@a) /* cast to pointer to work around bounds check */ sl# = (sl# : @a#)[:len] -> sl# ;; /* grow in factors of 1.5 */ nel = sl#.len while nel < len nel += (nel >> 2) + 1 ;; new = slalloc(nel) n = min(len, sl#.len) memblit((new : byte#), (sl# : byte#), n * sizeof(@a)) if sl#.len > 0 slfree(sl#) ;; sl# = new[:len] -> sl# } /* Grows a slice, filling new entries with zero bytes */ generic slzgrow = {sl : @a[:]#, len var oldlen var base oldlen = sl#.len slgrow(sl, len) base = ((sl# : byte#) : intptr) if oldlen < len memfill((sl#[oldlen:] : byte#), 0, (len - oldlen)*sizeof(@a)) ;; -> sl# } const slcap = {p var phdr phdr = ((p : size) - align(sizeof(slheader), Align) : slheader#) std.iassert(phdr.magic == (0xdeadbeefbadf00d : size), "corrupt memory\n") -> phdr.cap }