loa

commit fbfe5b87f9dcd82eca0a2df6971bac9dcaca62f9
parent 8f5f7a310b42fc1144b6696334a175c68a38cbb3
Author: Juan F. Meleiro <juan@juanmeleiro.mat.br>
Date:   Tue, 27 Feb 2024 13:58:10 -0300

Add interning library

Diffstat:
A
coding/interning.c
 | 
45
+++++++++++++++++++++++++++++++++++++++++++++
A
coding/interning.h
 | 
12
++++++++++++
A
coding/interning.test.c
 | 
26
++++++++++++++++++++++++++

3 files changed, 83 insertions(+), 0 deletions(-)
diff --git a/coding/interning.c b/coding/interning.c
@@ -0,0 +1,45 @@
+#include "interning.h"
+#include <stdbool.h>
+#include <assert.h>
+#include <string.h>
+
+static char **db      = NULL;
+static size_t cap     = 0;
+static size_t len     = 0;
+static bool initialized = false;
+
+void
+initialize(void)
+{
+	cap = 1;
+	db = malloc(cap * sizeof(char*));
+	initialized = true;
+}
+
+symbol
+append(char *name)
+{
+	assert(initialized);
+	if (len == cap)
+		db = realloc(db, (cap *= 2)*sizeof(char*));
+	assert(db);
+	db[len] = name;
+	return len++;
+}
+
+symbol
+intern(char *name)
+{
+	assert(initialized);
+	for (size_t i = 0; i < len; i++)
+		if (strcmp(name, db[i]) == 0)
+			return i;
+	return append(name);
+}
+
+char*
+repr(symbol s)
+{
+	assert(initialized);
+	return db[s];
+}
diff --git a/coding/interning.h b/coding/interning.h
@@ -0,0 +1,12 @@
+#include <stdlib.h>
+
+typedef size_t symbol;
+
+/* Guarantees:
+   - strcmp(repr(intern(s)), s) == 0
+   - intern(repr(s)) == s
+ */
+
+void initialize();
+symbol intern(char*);
+char* repr(symbol);
diff --git a/coding/interning.test.c b/coding/interning.test.c
@@ -0,0 +1,26 @@
+#include "interning.h"
+#include <stdbool.h>
+#include <assert.h>
+#include <string.h>
+
+bool
+test_repr_of_intern_is_iso()
+{
+	char *test = "abc";
+	return strcmp(repr(intern(test)), test) == 0;
+}
+
+bool
+test_intern_of_repr_is_id()
+{
+	char *test = "abc";
+	symbol s = intern(test);
+	return intern(repr(s)) == s;
+}
+
+int
+main() {
+	initialize();
+	assert(test_repr_of_intern_is_iso());
+	assert(test_intern_of_repr_is_id());
+}