asprintf: new asprintf module.

asprintf is a PITA to use, and it's not in POSIX anyway.  Provide
replacements, and also provide a nicer-to-use afmt() wrapper.

ccan/asprintf/LICENSE

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+../../licenses/BSD-MIT

ccan/asprintf/_info

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+#include <string.h>
+#include "config.h"
+
+/**
+ * asprintf - asprintf wrapper (and if necessary, implementation).
+ *
+ * This provides a convenient wrapper for asprintf, and also implements
+ * asprintf if necessary.
+ *
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ *
+ * License: MIT
+ *
+ * Example:
+ *	#include <ccan/asprintf/asprintf.h>
+ *	#include <unistd.h>
+ *	#include <err.h>
+ *
+ *	int main(int argc, char *argv[])
+ *	{
+ *		char *p = afmt("This program has %i arguments", argc);
+ *		int ret;
+ *
+ *		while ((ret = write(STDOUT_FILENO, p, strlen(p))) > 0) {
+ *			p += ret;
+ *			if (!*p)
+ *				exit(0);
+ *		}
+ *		err(1, "Writing to stdout");
+ *	}
+ */
+int main(int argc, char *argv[])
+{
+	/* Expect exactly one argument */
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		printf("ccan/compiler\n");
+		return 0;
+	}
+
+	return 1;
+}

ccan/asprintf/asprintf.c

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+#include <ccan/asprintf/asprintf.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+char *PRINTF_FMT(1, 2) afmt(const char *fmt, ...)
+{
+	va_list ap;
+	char *ptr;
+
+	va_start(ap, fmt);
+	/* The BSD version apparently sets ptr to NULL on fail.  GNU loses. */
+	if (vasprintf(&ptr, fmt, ap) < 0)
+		ptr = NULL;
+	va_end(ap);
+	return ptr;
+}
+
+#if !HAVE_ASPRINTF
+#include <stdarg.h>
+#include <stdlib.h>
+
+int vasprintf(char **strp, const char *fmt, va_list ap)
+{
+	int len;
+	va_list ap_copy;
+
+	/* We need to make a copy of ap, since it's a use-once. */
+	va_copy(ap_copy, ap);
+	len = vsnprintf(NULL, 0, fmt, ap_copy);
+	va_end(ap_copy);
+
+	/* Until version 2.0.6 glibc would return -1 on truncated output.
+	 * OTOH, they had asprintf. */
+	if (len < 0)
+		return -1;
+
+	*strp = malloc(len+1);
+	if (!*strp)
+		return -1;
+
+	return vsprintf(*strp, fmt, ap);
+}
+
+int asprintf(char **strp, const char *fmt, ...)
+{
+	va_list ap;
+	int len;
+
+	va_start(ap, fmt);
+	len = vasprintf(strp, fmt, ap);
+	va_end(ap);
+
+	return len;
+}
+#endif /* !HAVE_ASPRINTF */

ccan/asprintf/asprintf.h

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+#ifndef CCAN_ASPRINTF_H
+#define CCAN_ASPRINTF_H
+#include "config.h"
+#include <ccan/compiler/compiler.h>
+
+/**
+ * afmt - allocate and populate a string with the given format.
+ * @fmt: printf-style format.
+ *
+ * This is a simplified asprintf interface.  Returns NULL on error.
+ */
+char *PRINTF_FMT(1, 2) afmt(const char *fmt, ...);
+
+#if HAVE_ASPRINTF
+#include <stdio.h>
+#else
+#include <stdarg.h>
+/**
+ * asprintf - printf to a dynamically-allocated string.
+ * @strp: pointer to the string to allocate.
+ * @fmt: printf-style format.
+ *
+ * Returns -1 (and leaves @strp undefined) on an error.  Otherwise returns
+ * number of bytes printed into @strp.
+ *
+ * Example:
+ *	static char *greeting(const char *name)
+ *	{
+ *		char *str;
+ *		int len = asprintf(&str, "Hello %s", name);
+ *		if (len < 0)
+ *			return NULL;
+ *		return str;
+ *	}
+ */
+int PRINTF_FMT(2, 3) asprintf(char **strp, const char *fmt, ...);
+
+/**
+ * vasprintf - vprintf to a dynamically-allocated string.
+ * @strp: pointer to the string to allocate.
+ * @fmt: printf-style format.
+ *
+ * Returns -1 (and leaves @strp undefined) on an error.  Otherwise returns
+ * number of bytes printed into @strp.
+ */
+int vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+#endif /* CCAN_ASPRINTF_H */

ccan/asprintf/test/run.c

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+#include <ccan/asprintf/asprintf.h>
+/* Include the C files directly. */
+
+/* Override vasprintf for testing. */
+#if HAVE_ASPRINTF
+#define vasprintf my_vasprintf
+static int my_vasprintf(char **strp, const char *fmt, va_list ap);
+#else
+#include <stdio.h>
+#include <stdarg.h>
+#define vsnprintf my_vsnprintf
+static int my_vsnprintf(char *str, size_t size, const char *format, va_list ap);
+#endif
+
+#include <ccan/asprintf/asprintf.c>
+#include <ccan/tap/tap.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+static bool fail;
+
+#if HAVE_ASPRINTF
+#undef vasprintf
+static int my_vasprintf(char **strp, const char *fmt, va_list ap)
+{
+	if (fail) {
+		/* Set strp to crap. */
+		*strp = (char *)(long)1;
+		return -1;
+	}
+	return vasprintf(strp, fmt, ap);
+}
+#else
+#undef vsnprintf
+static int my_vsnprintf(char *str, size_t size, const char *format, va_list ap)
+{
+	if (fail) {
+		return -1;
+	}
+	return vsnprintf(str, size, format, ap);
+}
+#endif
+
+int main(void)
+{
+	char *p, nul = '\0';
+	int ret;
+
+	/* This is how many tests you plan to run */
+	plan_tests(8);
+
+	fail = false;
+	p = afmt("Test %u%cafter-nul", 1, nul);
+	ok1(p);
+	ok1(strlen(p) == strlen("Test 1"));
+	ok1(memcmp(p, "Test 1\0after-nul\0", 17) == 0);
+	free(p);
+
+	ret = asprintf(&p, "Test %u%cafter-nul", 1, nul);
+	ok1(ret == 16);
+	ok1(p);
+	ok1(strlen(p) == strlen("Test 1"));
+	ok1(memcmp(p, "Test 1\0after-nul\0", 17) == 0);
+	free(p);
+
+	fail = true;
+	p = afmt("Test %u%cafter-nul", 1, nul);
+	ok1(p == NULL);
+
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}