util: Create string_view tool to optimize memory usage

We are allocating heap memory to create tokens value, we can minimize the
number of allocations if we start using string_view.

We have other problems, right now the tokens value ownership are quite
unclear once the AST nodes also share the memory allocation done by
token_get_next_token function.

It's important to clarify we also have memory leaks on the current
implementation.  Hence, we are going to start using string_view to make
the memory management easier. :^)

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>

2 files changed, 87 insertions, 0 deletions

diff --git a/src/string_view.c b/src/string_view.c
new file mode 100644
index 0000000..d511e63
--- /dev/null
+++ b/src/string_view.c
@@ -0,0 +1,49 @@
+/*
+* Copyright (C) 2023 Johnny Richard
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#include "string_view.h"
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+string_view_t
+string_view_new(const char *str, int size)
+{
+  assert(str);
+
+  return (string_view_t) {
+    .size = size,
+    .str = str
+  };
+}
+
+string_view_t
+string_view_from_str(const char *str)
+{
+  return string_view_new(str, strlen(str));
+}
+
+bool
+string_view_to_str(string_view_t *sv, char *ret)
+{
+  return sprintf(ret, SVFMT, SVARG(sv)) < 0;
+}
+
+bool
+string_view_eq(string_view_t a, string_view_t b)
+{
+  return a.size == b.size && memcmp(a.str, b.str, a.size) == 0;
+}
diff --git a/src/string_view.h b/src/string_view.h
new file mode 100644
index 0000000..41094a2
--- /dev/null
+++ b/src/string_view.h
@@ -0,0 +1,38 @@
+/*
+* Copyright (C) 2023 Johnny Richard
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#ifndef STRING_VIEW
+#define STRING_VIEW
+
+#define SVFMT "%.*s"
+#define SVARG(sv) (sv)->size, (sv)->str
+
+#include <stdbool.h>
+
+typedef struct string_view_t {
+  const char *str;
+  int         size;
+} string_view_t;
+
+string_view_t string_view_new(const char *str, int size);
+
+string_view_t string_view_from_str(const char *str);
+
+bool string_view_to_str(string_view_t *sv, char *ret);
+
+bool string_view_eq(string_view_t a, string_view_t b);
+
+#endif /* STRING_VIEW */