@[has_globals]
module builtin

// v_memory_panic will be true, *only* when a call to malloc/realloc/vcalloc etc could not succeed.
// In that situation, functions that are registered with at_exit(), should be able to limit their
// activity accordingly, by checking this flag.
// The V compiler itself for example registers a function with at_exit(), for showing timers.
// Without a way to distinguish, that we are in a memory panic, that would just display a second panic,
// which would be less clear to the user.
__global v_memory_panic = false

@[noreturn]
fn _memory_panic(fname string, size isize) {
    v_memory_panic = true
    // Note: do not use string interpolation here at all, since string interpolation itself allocates
    eprint(fname)
    eprint('(')
    $if freestanding || vinix {
        eprint('size') // TODO: use something more informative here
    } $else {
        C.fprintf(C.stderr, c'%p', voidptr(size))
    }
    if size < 0 {
        eprint(' < 0')
    }
    eprintln(')')
    panic('memory allocation failure')
}

__global total_m = i64(0)
// malloc dynamically allocates a `n` bytes block of memory on the heap.
// malloc returns a `byteptr` pointing to the memory address of the allocated space.
// unlike the `calloc` family of functions - malloc will not zero the memory block.
@[unsafe]
pub fn malloc(n isize) &u8 {
    $if trace_malloc ? {
        total_m += n
        C.fprintf(C.stderr, c'_v_malloc %6d total %10d\n', n, total_m)
        // print_backtrace()
    }
    if n < 0 {
        _memory_panic(@FN, n)
    } else if n == 0 {
        return &u8(unsafe { nil })
    }
    mut res := &u8(unsafe { nil })
    $if prealloc {
        return unsafe { prealloc_malloc(n) }
    } $else $if vgc ? {
        unsafe {
            res = &u8(vgc_malloc(usize(n)))
        }
    } $else $if gcboehm ? {
        unsafe {
            res = C.GC_MALLOC(n)
        }
    } $else $if freestanding {
        // todo: is this safe to call malloc there? We export __malloc as malloc and it uses dlmalloc behind the scenes
        // so theoretically it is safe
        res = unsafe { __malloc(usize(n)) }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_malloc to allocate memory.
            // This ensures that we can later free the memory with _aligned_free
            // without needing to track whether the memory was originally allocated
            // by malloc or _aligned_malloc.
            res = unsafe { C._aligned_malloc(n, 1) }
        } $else {
            res = unsafe { C.malloc(n) }
        }
    }
    if res == 0 {
        _memory_panic(@FN, n)
    }
    $if debug_malloc ? {
        // Fill in the memory with something != 0 i.e. `M`, so it is easier to spot
        // when the calling code wrongly relies on it being zeroed.
        unsafe { C.memset(res, 0x4D, n) }
    }
    return res
}

@[unsafe]
pub fn malloc_noscan(n isize) &u8 {
    $if trace_malloc ? {
        total_m += n
        C.fprintf(C.stderr, c'malloc_noscan %6d total %10d\n', n, total_m)
        // print_backtrace()
    }
    if n < 0 {
        _memory_panic(@FN, n)
    }
    mut res := &u8(unsafe { nil })
    $if prealloc {
        return unsafe { prealloc_malloc(n) }
    } $else $if vgc ? {
        unsafe {
            res = &u8(vgc_malloc_noscan(usize(n)))
        }
    } $else $if gcboehm ? {
        $if gcboehm_opt ? {
            unsafe {
                res = C.GC_MALLOC_ATOMIC(n)
            }
        } $else {
            unsafe {
                res = C.GC_MALLOC(n)
            }
        }
    } $else $if freestanding {
        res = unsafe { __malloc(usize(n)) }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_malloc to allocate memory.
            // This ensures that we can later free the memory with _aligned_free
            // without needing to track whether the memory was originally allocated
            // by malloc or _aligned_malloc.
            res = unsafe { C._aligned_malloc(n, 1) }
        } $else {
            res = unsafe { C.malloc(n) }
        }
    }
    if res == 0 {
        _memory_panic(@FN, n)
    }
    $if debug_malloc ? {
        // Fill in the memory with something != 0 i.e. `M`, so it is easier to spot
        // when the calling code wrongly relies on it being zeroed.
        unsafe { C.memset(res, 0x4D, n) }
    }
    return res
}

@[unsafe]
fn malloc_uninit(n isize) &u8 {
    if n < 0 {
        _memory_panic(@FN, n)
    } else if n == 0 {
        return &u8(unsafe { nil })
    }
    $if vgc ? {
        return unsafe { &u8(vgc_malloc_typed_opts(usize(n), 0, 0, false)) }
    }
    return malloc(n)
}

@[unsafe]
fn malloc_noscan_uninit(n isize) &u8 {
    if n < 0 {
        _memory_panic(@FN, n)
    } else if n == 0 {
        return &u8(unsafe { nil })
    }
    $if vgc ? {
        return unsafe { &u8(vgc_malloc_noscan_opts(usize(n), false)) }
    }
    return malloc_noscan(n)
}

@[inline]
fn __at_least_one(how_many u64) u64 {
    // handle the case for allocating memory for empty structs, which have sizeof(EmptyStruct) == 0
    // in this case, just allocate a single byte, avoiding the panic for malloc(0)
    if how_many == 0 {
        return 1
    }
    return how_many
}

// malloc_uncollectable dynamically allocates a `n` bytes block of memory
// on the heap, which will NOT be garbage-collected (but its contents will).
@[unsafe]
pub fn malloc_uncollectable(n isize) &u8 {
    $if trace_malloc ? {
        total_m += n
        C.fprintf(C.stderr, c'malloc_uncollectable %6d total %10d\n', n, total_m)
        // print_backtrace()
    }
    if n < 0 {
        _memory_panic(@FN, n)
    }

    mut res := &u8(unsafe { nil })
    $if prealloc {
        return unsafe { prealloc_malloc(n) }
    } $else $if vgc ? {
        unsafe {
            res = &u8(vgc_malloc(usize(n)))
        }
    } $else $if gcboehm ? {
        unsafe {
            res = C.GC_MALLOC_UNCOLLECTABLE(n)
        }
    } $else $if freestanding {
        res = unsafe { __malloc(usize(n)) }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_malloc to allocate memory.
            // This ensures that we can later free the memory with _aligned_free
            // without needing to track whether the memory was originally allocated
            // by malloc or _aligned_malloc.
            res = unsafe { C._aligned_malloc(n, 1) }
        } $else {
            res = unsafe { C.malloc(n) }
        }
    }
    if res == 0 {
        _memory_panic(@FN, n)
    }
    $if debug_malloc ? {
        // Fill in the memory with something != 0 i.e. `M`, so it is easier to spot
        // when the calling code wrongly relies on it being zeroed.
        unsafe { C.memset(res, 0x4D, n) }
    }
    return res
}

// v_realloc resizes the memory block `b` with `n` bytes.
// The `b byteptr` must be a pointer to an existing memory block
// previously allocated with `malloc` or `vcalloc`.
// Please, see also realloc_data, and use it instead if possible.
@[unsafe]
pub fn v_realloc(b &u8, n isize) &u8 {
    $if trace_realloc ? {
        C.fprintf(C.stderr, c'v_realloc %6d\n', n)
    }
    mut new_ptr := &u8(unsafe { nil })
    $if prealloc {
        unsafe {
            new_ptr = malloc(n)
            C.memcpy(new_ptr, b, n)
        }
        return new_ptr
    } $else $if vgc ? {
        new_ptr = unsafe { &u8(vgc_realloc(b, usize(n))) }
    } $else $if gcboehm ? {
        new_ptr = unsafe { C.GC_REALLOC(b, n) }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_realloc to reallocate memory.
            // This ensures that we can later free the memory with _aligned_free
            // without needing to track whether the memory was originally allocated
            // by malloc or _aligned_malloc/_aligned_realloc.
            new_ptr = unsafe { C._aligned_realloc(b, n, 1) }
        } $else {
            new_ptr = unsafe { C.realloc(b, n) }
        }
    }
    if new_ptr == 0 {
        _memory_panic(@FN, n)
    }
    return new_ptr
}

// realloc_data resizes the memory block pointed by `old_data` to `new_size`
// bytes. `old_data` must be a pointer to an existing memory block, previously
// allocated with `malloc` or `vcalloc`, of size `old_data`.
// realloc_data returns a pointer to the new location of the block.
// Note: if you know the old data size, it is preferable to call `realloc_data`,
// instead of `v_realloc`, at least during development, because `realloc_data`
// can make debugging easier, when you compile your program with
// `-d debug_realloc`.
@[unsafe]
pub fn realloc_data(old_data &u8, old_size int, new_size int) &u8 {
    $if trace_realloc ? {
        C.fprintf(C.stderr, c'realloc_data old_size: %6d new_size: %6d\n', old_size, new_size)
    }
    $if prealloc {
        return unsafe { prealloc_realloc(old_data, old_size, new_size) }
    }
    $if debug_realloc ? {
        // Note: this is slower, but helps debugging memory problems.
        // The main idea is to always force reallocating:
        // 1) allocate a new memory block
        // 2) copy the old to the new
        // 3) fill the old with 0x57 (`W`)
        // 4) free the old block
        // => if there is still a pointer to the old block somewhere
        //    it will point to memory that is now filled with 0x57.
        unsafe {
            new_ptr := malloc(new_size)
            min_size := if old_size < new_size { old_size } else { new_size }
            C.memcpy(new_ptr, old_data, min_size)
            C.memset(old_data, 0x57, old_size)
            free(old_data)
            return new_ptr
        }
    }
    mut nptr := &u8(unsafe { nil })
    $if vgc ? {
        nptr = unsafe { &u8(vgc_realloc(old_data, usize(new_size))) }
    } $else $if gcboehm ? {
        nptr = unsafe { C.GC_REALLOC(old_data, new_size) }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_realloc to reallocate memory.
            // This ensures that we can later free the memory with _aligned_free
            // without needing to track whether the memory was originally allocated
            // by malloc or _aligned_malloc/_aligned_realloc.
            nptr = unsafe { C._aligned_realloc(old_data, new_size, 1) }
        } $else {
            nptr = unsafe { C.realloc(old_data, new_size) }
        }
    }
    if nptr == 0 {
        _memory_panic(@FN, isize(new_size))
    }
    return nptr
}

// vcalloc dynamically allocates a zeroed `n` bytes block of memory on the heap.
// vcalloc returns a `byteptr` pointing to the memory address of the allocated space.
// vcalloc checks for negative values given in `n`.
pub fn vcalloc(n isize) &u8 {
    $if trace_vcalloc ? {
        total_m += n
        C.fprintf(C.stderr, c'vcalloc %6d total %10d\n', n, total_m)
    }
    if n < 0 {
        _memory_panic(@FN, n)
    } else if n == 0 {
        return &u8(unsafe { nil })
    }
    $if prealloc {
        return unsafe { prealloc_calloc(n) }
    } $else $if vgc ? {
        return unsafe { &u8(vgc_calloc(usize(n))) }
    } $else $if gcboehm ? {
        return unsafe { &u8(C.GC_MALLOC(n)) }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_malloc to allocate memory.
            // This ensures that we can later free the memory with _aligned_free
            // without needing to track whether the memory was originally allocated
            // by malloc or _aligned_malloc/_aligned_realloc/_aligned_recalloc.
            ptr := unsafe { C._aligned_malloc(n, 1) }
            if ptr != &u8(unsafe { nil }) {
                unsafe { C.memset(ptr, 0, n) }
            }
            return ptr
        } $else {
            return unsafe { C.calloc(1, n) }
        }
    }
    return &u8(unsafe { nil }) // not reached, TODO: remove when V's checker is improved
}

// special versions of the above that allocate memory which is not scanned
// for pointers (but is collected) when the Boehm garbage collection is used
pub fn vcalloc_noscan(n isize) &u8 {
    $if trace_vcalloc ? {
        total_m += n
        C.fprintf(C.stderr, c'vcalloc_noscan %6d total %10d\n', n, total_m)
    }
    $if prealloc {
        return unsafe { prealloc_calloc(n) }
    } $else $if vgc ? {
        if n < 0 {
            _memory_panic(@FN, n)
        }
        return unsafe { &u8(vgc_calloc(usize(n))) }
    } $else $if gcboehm ? {
        if n < 0 {
            _memory_panic(@FN, n)
        }
        $if gcboehm_opt ? {
            res := unsafe { C.GC_MALLOC_ATOMIC(n) }
            unsafe { C.memset(res, 0, n) }
            return &u8(res)
        } $else {
            res := unsafe { C.GC_MALLOC(n) }
            return &u8(res)
        }
    } $else {
        return unsafe { vcalloc(n) }
    }
    return &u8(unsafe { nil }) // not reached, TODO: remove when V's checker is improved
}

// free allows for manually freeing memory allocated at the address `ptr`.
@[unsafe]
pub fn free(ptr voidptr) {
    $if trace_free ? {
        C.fprintf(C.stderr, c'free ptr: %p\n', ptr)
    }
    $if builtin_free_nop ? {
        return
    }
    if ptr == unsafe { 0 } {
        $if trace_free_nulls ? {
            C.fprintf(C.stderr, c'free null ptr\n', ptr)
        }
        $if trace_free_nulls_break ? {
            break_if_debugger_attached()
        }
        return
    }
    // `none__` is a process-wide singleton IError used by option/results to
    // represent "no error object". Self-hosted builds can still route that
    // sentinel through explicit cleanup paths under `-gc none`, so ignore it.
    none_err := &C.IError(&none__)
    if ptr == none_err._object {
        return
    }
    $if prealloc {
        return
    } $else $if vgc ? {
        // VGC: explicit free is optional (GC will collect unreachable objects).
        // But hint the allocator for faster reuse.
        vgc_free(ptr)
    } $else $if gcboehm ? {
        // It is generally better to leave it to Boehm's gc to free things.
        // Calling C.GC_FREE(ptr) was tried initially, but does not work
        // well with programs that do manual management themselves.
        //
        // The exception is doing leak detection for manual memory management:
        $if gcboehm_leak ? {
            unsafe { C.GC_FREE(ptr) }
        }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_free to free memory.
            unsafe { C._aligned_free(ptr) }
        } $else {
            C.free(ptr)
        }
    }
}

// memdup dynamically allocates a `sz` bytes block of memory on the heap
// memdup then copies the contents of `src` into the allocated space and
// returns a pointer to the newly allocated space.
@[unsafe]
pub fn memdup(src voidptr, sz isize) voidptr {
    $if trace_memdup ? {
        C.fprintf(C.stderr, c'memdup size: %10d\n', sz)
    }
    if sz == 0 {
        return vcalloc(1)
    }
    $if vgc ? {
        return vgc_memdup(src, sz)
    }
    unsafe {
        mem := malloc(sz)
        return C.memcpy(mem, src, sz)
    }
}

@[unsafe]
pub fn memdup_noscan(src voidptr, sz isize) voidptr {
    $if trace_memdup ? {
        C.fprintf(C.stderr, c'memdup_noscan size: %10d\n', sz)
    }
    if sz == 0 {
        return vcalloc_noscan(1)
    }
    $if vgc ? {
        return vgc_memdup_noscan(src, sz)
    }
    unsafe {
        mem := malloc_noscan(sz)
        return C.memcpy(mem, src, sz)
    }
}

// memdup_uncollectable dynamically allocates a `sz` bytes block of memory
// on the heap, which will NOT be garbage-collected (but its contents will).
// memdup_uncollectable then copies the contents of `src` into the allocated
// space and returns a pointer to the newly allocated space.
@[unsafe]
pub fn memdup_uncollectable(src voidptr, sz isize) voidptr {
    $if trace_memdup ? {
        C.fprintf(C.stderr, c'memdup_uncollectable size: %10d\n', sz)
    }
    if sz == 0 {
        return vcalloc(1)
    }
    unsafe {
        mem := malloc_uncollectable(sz)
        return C.memcpy(mem, src, sz)
    }
}

// memdup_align dynamically allocates a memory block of `sz` bytes on the heap,
// copies the contents from `src` into the allocated space, and returns a pointer
// to the newly allocated memory. The returned pointer is aligned to the specified `align` boundary.
//   - `align` must be a power of two and at least 1
//   - `sz` must be non-negative
//   - The memory regions should not overlap
@[unsafe]
pub fn memdup_align(src voidptr, sz isize, align isize) voidptr {
    $if trace_memdup ? {
        C.fprintf(C.stderr, c'memdup_align size: %10d align: %10d\n', sz, align)
    }
    if sz == 0 {
        return vcalloc(1)
    }
    n := sz
    $if trace_malloc ? {
        total_m += n
        C.fprintf(C.stderr, c'_v_memdup_align %6d total %10d\n', n, total_m)
        // print_backtrace()
    }
    if n < 0 {
        _memory_panic(@FN, n)
    }
    mut res := &u8(unsafe { nil })
    $if prealloc {
        res = prealloc_malloc_align(n, align)
    } $else $if gcboehm ? {
        unsafe {
            res = C.GC_memalign(align, n)
        }
    } $else $if freestanding {
        // todo: is this safe to call malloc there? We export __malloc as malloc and it uses dlmalloc behind the scenes
        // so theoretically it is safe
        panic('memdup_align is not implemented with -freestanding')
        res = unsafe { __malloc(usize(n)) }
    } $else {
        $if windows {
            // Warning! On windows, we always use _aligned_malloc to allocate memory.
            // This ensures that we can later free the memory with _aligned_free
            // without needing to track whether the memory was originally allocated
            // by malloc or _aligned_malloc.
            res = unsafe { C._aligned_malloc(n, align) }
        } $else {
            res = unsafe { C.aligned_alloc(align, n) }
        }
    }
    if res == 0 {
        _memory_panic(@FN, n)
    }
    $if debug_malloc ? {
        // Fill in the memory with something != 0 i.e. `M`, so it is easier to spot
        // when the calling code wrongly relies on it being zeroed.
        unsafe { C.memset(res, 0x4D, n) }
    }
    return C.memcpy(res, src, sz)
}

// GCHeapUsage contains stats about the current heap usage of your program.
pub struct GCHeapUsage {
pub:
    heap_size      usize
    free_bytes     usize
    total_bytes    usize
    unmapped_bytes usize
    bytes_since_gc usize
}

// gc_heap_usage returns the info about heap usage.
pub fn gc_heap_usage() GCHeapUsage {
    $if vgc ? {
        heap_size, free_bytes, total_bytes, unmapped, bytes_since := vgc_heap_usage()
        return GCHeapUsage{
            heap_size:      heap_size
            free_bytes:     free_bytes
            total_bytes:    total_bytes
            unmapped_bytes: unmapped
            bytes_since_gc: bytes_since
        }
    } $else $if gcboehm ? {
        mut res := GCHeapUsage{}
        C.GC_get_heap_usage_safe(&res.heap_size, &res.free_bytes, &res.unmapped_bytes,
            &res.bytes_since_gc, &res.total_bytes)
        return res
    } $else {
        return GCHeapUsage{}
    }
}

// gc_memory_use returns the total memory use in bytes by all allocated blocks.
pub fn gc_memory_use() usize {
    $if vgc ? {
        return vgc_memory_use()
    } $else $if gcboehm ? {
        return C.GC_get_memory_use()
    } $else {
        return 0
    }
}