github.com/tinygo-org/tinygo@v0.31.3-0.20240404173401-90b0bf646c27/src/runtime/arch_tinygowasm_malloc.go (about)

     1  //go:build tinygo.wasm && !(custommalloc || wasm_unknown)
     2  
     3  package runtime
     4  
     5  import "unsafe"
     6  
     7  // The below functions override the default allocator of wasi-libc. This ensures
     8  // code linked from other languages can allocate memory without colliding with
     9  // our GC allocations.
    10  
    11  var allocs = make(map[uintptr][]byte)
    12  
    13  //export malloc
    14  func libc_malloc(size uintptr) unsafe.Pointer {
    15  	if size == 0 {
    16  		return nil
    17  	}
    18  	buf := make([]byte, size)
    19  	ptr := unsafe.Pointer(&buf[0])
    20  	allocs[uintptr(ptr)] = buf
    21  	return ptr
    22  }
    23  
    24  //export free
    25  func libc_free(ptr unsafe.Pointer) {
    26  	if ptr == nil {
    27  		return
    28  	}
    29  	if _, ok := allocs[uintptr(ptr)]; ok {
    30  		delete(allocs, uintptr(ptr))
    31  	} else {
    32  		panic("free: invalid pointer")
    33  	}
    34  }
    35  
    36  //export calloc
    37  func libc_calloc(nmemb, size uintptr) unsafe.Pointer {
    38  	// No difference between calloc and malloc.
    39  	return libc_malloc(nmemb * size)
    40  }
    41  
    42  //export realloc
    43  func libc_realloc(oldPtr unsafe.Pointer, size uintptr) unsafe.Pointer {
    44  	if size == 0 {
    45  		libc_free(oldPtr)
    46  		return nil
    47  	}
    48  
    49  	// It's hard to optimize this to expand the current buffer with our GC, but
    50  	// it is theoretically possible. For now, just always allocate fresh.
    51  	buf := make([]byte, size)
    52  
    53  	if oldPtr != nil {
    54  		if oldBuf, ok := allocs[uintptr(oldPtr)]; ok {
    55  			copy(buf, oldBuf)
    56  			delete(allocs, uintptr(oldPtr))
    57  		} else {
    58  			panic("realloc: invalid pointer")
    59  		}
    60  	}
    61  
    62  	ptr := unsafe.Pointer(&buf[0])
    63  	allocs[uintptr(ptr)] = buf
    64  	return ptr
    65  }