Arena Allocator

include/prism/allocator.h

@@ -0,0 +1,46 @@
+# /**
+ * @file allocator.h
+ *
+ * An arena allocator.
+ */
+#ifndef PRISM_ALLOCATOR_H
+#define PRISM_ALLOCATOR_H
+
+#include "prism/defines.h"
+#include <assert.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+typedef struct pm_allocator_page {
+    struct pm_allocator_page *next;
+    char *start;
+    char *current;
+    char *end;
+} pm_allocator_page_t;
+
+typedef struct pm_allocator {
+    pm_allocator_page_t head;
+    pm_allocator_page_t *tail;
+} pm_allocator_t;
+
+/**
+ * Initialize an allocator with the given capacity.
+ */
+void pm_allocator_init(pm_allocator_t *allocator, size_t capacity);
+
+/**
+ * Allocate memory from the given allocator.
+ */
+void * pm_allocator_arena_alloc(pm_allocator_t *allocator, size_t size, size_t alignment);
+
+/**
+ * Allocate memory from the given allocator and zero out the memory.
+ */
+void * pm_allocator_arena_calloc(pm_allocator_t *allocator, size_t count, size_t size, size_t alignment);
+
+/**
+ * Frees the internal memory associated with the allocator.
+ */
+void pm_allocator_free(pm_allocator_t *allocator);
+
+#endif

include/prism/defines.h

@@ -164,6 +164,7 @@
  * #endif
  * ```
  */
+
 #ifdef PRISM_XALLOCATOR
     #include "prism_xallocator.h"
 #else

include/prism/node.h

@@ -7,6 +7,7 @@
 #define PRISM_NODE_H
 
 #include "prism/defines.h"
+#include "prism/allocator.h"
 #include "prism/parser.h"
 #include "prism/util/pm_buffer.h"
 
@@ -23,30 +24,23 @@
  * @param list The list to append to.
  * @param node The node to append.
  */
-void pm_node_list_append(pm_node_list_t *list, pm_node_t *node);
+void pm_node_list_append(pm_allocator_t *allocator, pm_node_list_t *list, pm_node_t *node);
 
 /**
  * Prepend a new node onto the beginning of the node list.
  *
  * @param list The list to prepend to.
  * @param node The node to prepend.
  */
-void pm_node_list_prepend(pm_node_list_t *list, pm_node_t *node);
+void pm_node_list_prepend(pm_allocator_t *allocator, pm_node_list_t *list, pm_node_t *node);
 
 /**
  * Concatenate the given node list onto the end of the other node list.
  *
  * @param list The list to concatenate onto.
  * @param other The list to concatenate.
  */
-void pm_node_list_concat(pm_node_list_t *list, pm_node_list_t *other);
-
-/**
- * Free the internal memory associated with the given node list.
- *
- * @param list The list to free.
- */
-void pm_node_list_free(pm_node_list_t *list);
+void pm_node_list_concat(pm_allocator_t *allocator, pm_node_list_t *list, pm_node_list_t *other);
 
 /**
  * Deallocate a node and all of its children.

include/prism/parser.h

@@ -7,6 +7,7 @@
 #define PRISM_PARSER_H
 
 #include "prism/defines.h"
+#include "prism/allocator.h"
 #include "prism/ast.h"
 #include "prism/encoding.h"
 #include "prism/options.h"
@@ -581,6 +582,12 @@ typedef struct pm_scope {
     /** A pointer to the previous scope in the linked list. */
     struct pm_scope *previous;
 
+    /**
+     * This allocator is responsible for allocating the space for the list of
+     * the locals and the list of implicit parameters in the scope.
+     */
+    pm_allocator_t allocator;
+
     /** The IDs of the locals in the given scope. */
     pm_locals_t locals;
 
@@ -645,6 +652,12 @@ struct pm_parser {
      */
     uint32_t node_id;
 
+    /** The allocator used to allocate nodes and their fields. */
+    pm_allocator_t allocator;
+
+    /** The allocator used to allocate lists of block exits. */
+    pm_allocator_t block_exits_allocator;
+
     /** The current state of the lexer. */
     pm_lex_state_t lex_state;
 

include/prism/util/pm_constant_pool.h

@@ -11,6 +11,7 @@
 #define PRISM_CONSTANT_POOL_H
 
 #include "prism/defines.h"
+#include "prism/allocator.h"
 
 #include <assert.h>
 #include <stdbool.h>
@@ -54,10 +55,11 @@ void pm_constant_id_list_init(pm_constant_id_list_t *list);
 /**
  * Initialize a list of constant ids with a given capacity.
  *
+ * @param allocator The allocator to use to allocate space for the list.
  * @param list The list to initialize.
  * @param capacity The initial capacity of the list.
  */
-void pm_constant_id_list_init_capacity(pm_constant_id_list_t *list, size_t capacity);
+void pm_constant_id_list_init_capacity(pm_allocator_t *allocator, pm_constant_id_list_t *list, size_t capacity);
 
 /**
  * Append a constant id to a list of constant ids. Returns false if any

include/prism/util/pm_integer.h

@@ -7,6 +7,7 @@
 #define PRISM_NUMBER_H
 
 #include "prism/defines.h"
+#include "prism/allocator.h"
 #include "prism/util/pm_buffer.h"
 
 #include <assert.h>
@@ -77,12 +78,13 @@ typedef enum {
  * has already been validated, as internal validation checks are not performed
  * here.
  *
+ * @param allocator The allocator to use to allocate memory for the integer.
  * @param integer The integer to parse into.
  * @param base The base of the integer.
  * @param start The start of the string.
  * @param end The end of the string.
  */
-void pm_integer_parse(pm_integer_t *integer, pm_integer_base_t base, const uint8_t *start, const uint8_t *end);
+void pm_integer_parse(pm_allocator_t *allocator, pm_integer_t *integer, pm_integer_base_t base, const uint8_t *start, const uint8_t *end);
 
 /**
  * Compare two integers. This function returns -1 if the left integer is less

include/prism/util/pm_string.h

@@ -7,6 +7,7 @@
 #define PRISM_STRING_H
 
 #include "prism/defines.h"
+#include "prism/allocator.h"
 
 #include <assert.h>
 #include <errno.h>
@@ -150,7 +151,7 @@ PRISM_EXPORTED_FUNCTION pm_string_init_result_t pm_string_file_init(pm_string_t
  *
  * @param string The string to ensure is owned.
  */
-void pm_string_ensure_owned(pm_string_t *string);
+void pm_string_ensure_owned(pm_allocator_t *allocator, pm_string_t *string);
 
 /**
  * Compare the underlying lengths and bytes of two strings. Returns 0 if the

src/allocator.c

@@ -0,0 +1,120 @@
+#include "prism/allocator.h"
+
+#define PM_ALLOCATOR_CAPACITY_DEFAULT 4096
+
+/**
+ * Initialize an allocator with the given capacity.
+ */
+void
+pm_allocator_init(pm_allocator_t *allocator, size_t capacity) {
+    char *memory = xmalloc(capacity);
+    if (memory == NULL) {
+        fprintf(stderr, "[pm_allocator_init] failed to allocate memory\n");
+        abort();
+    }
+
+    *allocator = (pm_allocator_t) {
+        .head = {
+            .next = NULL,
+            .start = memory,
+            .current = memory,
+            .end = memory + capacity
+        },
+        .tail = &allocator->head
+    };
+}
+
+/**
+ * Allocate memory from the given allocator.
+ */
+void *
+pm_allocator_arena_alloc(pm_allocator_t *allocator, size_t size, size_t alignment) {
+    assert(size > 0);
+
+    char *result = allocator->tail->current;
+    uintptr_t delta = 0;
+    uintptr_t current = (uintptr_t) allocator->tail->current;
+    if (current % alignment != 0) {
+        delta = alignment - (current % alignment);
+    }
+    result += delta;
+
+    char *next = result + size;
+
+    if (next >= allocator->tail->end) {
+        size_t next_capacity = PM_ALLOCATOR_CAPACITY_DEFAULT;
+
+        // In case the requested size is larger than our default capacity, scale
+        // up just this node in the linked list to fit the allocation.
+        if (size > next_capacity) next_capacity = size;
+
+        char *memory = xmalloc(sizeof(pm_allocator_page_t) + next_capacity);
+        if (memory == NULL) {
+            fprintf(stderr, "[pm_allocator_arena_alloc] failed to allocate memory\n");
+            abort();
+        }
+
+        pm_allocator_page_t *next_allocator_page = (pm_allocator_page_t *) memory;
+        char *start = memory + sizeof(pm_allocator_page_t);
+
+        // Assume the alignment is correct because malloc should give us back
+        // the most relaxed alignment possible.
+        assert(((uintptr_t) start) % alignment == 0);
+
+        *next_allocator_page = (pm_allocator_page_t) {
+            .next = NULL,
+            .start = start,
+            .current = NULL, // set at the end
+            .end = start + next_capacity
+        };
+
+        allocator->tail->next = next_allocator_page;
+        allocator->tail = next_allocator_page;
+
+        result = allocator->tail->start;
+        next = result + size;
+    }
+
+    allocator->tail->current = next;
+    return result;
+}
+
+/**
+ * Allocate memory from the given allocator and zero out the memory.
+ */
+void *
+pm_allocator_arena_calloc(pm_allocator_t *allocator, size_t count, size_t size, size_t alignment) {
+    assert(size > 0);
+
+    size_t product = count * size;
+    assert(product / size == count);
+
+    void *memory = pm_allocator_arena_alloc(allocator, product, alignment);
+    memset(memory, 0, product);
+
+    return memory;
+}
+
+/**
+ * Frees the internal memory associated with the allocator.
+ */
+void pm_allocator_free(pm_allocator_t *allocator) {
+    bool top_level = true;
+
+    for (pm_allocator_page_t *current = &allocator->head; current != NULL;) {
+        pm_allocator_page_t *previous = current;
+        current = current->next;
+
+        // If the memory block is immediately after the allocation of the
+        // allocator itself, then it came from pm_allocator_arena_alloc, so we
+        // should free it. Otherwise we assume it was embedded into another
+        // struct or allocated on the stack.
+        if (top_level) {
+            free(previous->start);
+        } else {
+            free(previous);
+        }
+
+        top_level = false;
+    }
+}