From 86f852cd76cf92a4b08b59b127cc954420f95744 Mon Sep 17 00:00:00 2001
From: Matthew Sotoudeh <matthew@masot.net>
Date: Mon, 31 Jul 2023 13:53:16 -0700
Subject: share more code between the C examples

---
 c/string_helpers.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 c/string_helpers.c

(limited to 'c/string_helpers.c')

diff --git a/c/string_helpers.c b/c/string_helpers.c
new file mode 100644
index 0000000..636bad3
--- /dev/null
+++ b/c/string_helpers.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <stdarg.h>
+
+static char *sbuild(char *format, ...) {
+    // (1) overapproximate the length of the string. adapted from man va_start
+    unsigned long max_len = 1;
+    char *s;
+    va_list ap;
+    va_start(ap, format);
+    for (char *c = format; *c; c++) {
+        if (*c != '%') {
+            max_len++;
+            continue;
+        }
+
+        switch (*(++c)) {
+        case 's':
+            s = va_arg(ap, char*);
+            max_len += strlen(s);
+            break;
+        case 'l': // not quite accurate
+            va_arg(ap, unsigned long);
+            max_len += 64;
+            break;
+        case 'd':
+            va_arg(ap, int);
+            max_len += 32;
+            break;
+        case 'u':
+            va_arg(ap, unsigned);
+            max_len += 32;
+            break;
+        case 'f':
+            va_arg(ap, double);
+            max_len += 64;
+            break;
+        default: assert(0);
+        }
+    }
+    va_end(ap);
+
+    char *str = calloc(max_len, sizeof(char));
+    va_list ap_;
+    va_start(ap_, format);
+    vsprintf(str, format, ap_);
+    va_end(ap_);
+    return str;
+}
-- 
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