added truc

parser/nnsrc/wasm/stdlib.c

@@ -0,0 +1,109 @@
+// This file implements a very simple allocator for external scanners running
+// in WASM. Allocation is just bumping a static pointer and growing the heap
+// as needed, and freeing is mostly a noop. But in the special case of freeing
+// the last-allocated pointer, we'll reuse that pointer again.
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+extern void tree_sitter_debug_message(const char *, size_t);
+
+#define PAGESIZE 0x10000
+#define MAX_HEAP_SIZE (4 * 1024 * 1024)
+
+typedef struct {
+  size_t size;
+  char data[0];
+} Region;
+
+static Region *heap_end = NULL;
+static Region *heap_start = NULL;
+static Region *next = NULL;
+
+// Get the region metadata for the given heap pointer.
+static inline Region *region_for_ptr(void *ptr) {
+  return ((Region *)ptr) - 1;
+}
+
+// Get the location of the next region after the given region,
+// if the given region had the given size.
+static inline Region *region_after(Region *self, size_t len) {
+  char *address = self->data + len;
+  char *aligned = (char *)((uintptr_t)(address + 3) & ~0x3);
+  return (Region *)aligned;
+}
+
+static void *get_heap_end() {
+  return (void *)(__builtin_wasm_memory_size(0) * PAGESIZE);
+}
+
+static int grow_heap(size_t size) {
+  size_t new_page_count = ((size - 1) / PAGESIZE) + 1;
+  return __builtin_wasm_memory_grow(0, new_page_count) != SIZE_MAX;
+}
+
+// Clear out the heap, and move it to the given address.
+void reset_heap(void *new_heap_start) {
+  heap_start = new_heap_start;
+  next = new_heap_start;
+  heap_end = get_heap_end();
+}
+
+void *malloc(size_t size) {
+  Region *region_end = region_after(next, size);
+
+  if (region_end > heap_end) {
+    if ((char *)region_end - (char *)heap_start > MAX_HEAP_SIZE) {
+      return NULL;
+    }
+    if (!grow_heap(size)) return NULL;
+    heap_end = get_heap_end();
+  }
+
+  void *result = &next->data;
+  next->size = size;
+  next = region_end;
+
+  return result;
+}
+
+void free(void *ptr) {
+  if (ptr == NULL) return;
+
+  Region *region = region_for_ptr(ptr);
+  Region *region_end = region_after(region, region->size);
+
+  // When freeing the last allocated pointer, re-use that
+  // pointer for the next allocation.
+  if (region_end == next) {
+    next = region;
+  }
+}
+
+void *calloc(size_t count, size_t size) {
+  void *result = malloc(count * size);
+  memset(result, 0, count * size);
+  return result;
+}
+
+void *realloc(void *ptr, size_t new_size) {
+  if (ptr == NULL) {
+    return malloc(new_size);
+  }
+
+  Region *region = region_for_ptr(ptr);
+  Region *region_end = region_after(region, region->size);
+
+  // When reallocating the last allocated region, return
+  // the same pointer, and skip copying the data.
+  if (region_end == next) {
+    next = region;
+    return malloc(new_size);
+  }
+
+  void *result = malloc(new_size);
+  memcpy(result, &region->data, region->size);
+  return result;
+}