Added a test program for the special features of snprintf().

diff --git a/testcode/lib/snprintf-test.c b/testcode/lib/snprintf-test.c
new file mode 100644 (file)
index 0000000..d3af47d
--- /dev/null
+++ b/testcode/lib/snprintf-test.c
@@ -0,0 +1,144 @@
+/*
+** Test a function that formats and writes characters into a string buffer.
+** This program does not test formatting.  It tests some behaviors that are
+** specific to the buffer.  It tests that certain conditions are handled
+** properly.
+**
+** 2015-07-17, Greg King
+*/
+
+#include <conio.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+static const char format[] = "1234567890\nabcdefghijklmnopqrstuvwxyz\n%u\n%s\n\n";
+#define FORMAT_SIZE (sizeof format - 2u - 2u - 1u)
+
+#define arg1 12345u
+#define ARG1_SIZE (5u)
+
+static const char arg2[] = "!@#$%^&*()-+";
+#define ARG2_SIZE (sizeof arg2 - 1u)
+
+#define STRING_SIZE (FORMAT_SIZE + ARG1_SIZE + ARG2_SIZE)
+
+static char buf[256];
+static int size;
+
+
+static void fillbuf(void)
+{
+    memset(buf, 0xFF, sizeof buf - 1u);
+    buf[sizeof buf - 1u] = '\0';
+}
+
+
+unsigned char main(void)
+{
+    static unsigned char failures = 0;
+
+    /* Show what sprintf() should create. */
+
+    if ((size = printf(format, arg1, arg2)) != STRING_SIZE) {
+        ++failures;
+        printf("printf() gave the wrong size: %d.\n", size);
+    }
+
+    /* Test the normal behavior of sprintf(). */
+
+    fillbuf();
+    size = sprintf(buf, format, arg1, arg2);
+    fputs(buf, stdout);
+    if (size != STRING_SIZE) {
+        ++failures;
+        printf("sprintf() gave the wrong size: %d.\n", size);
+    }
+
+    /* Test the normal behavior of snprintf(). */
+
+    fillbuf();
+    size = snprintf(buf, sizeof buf, format, arg1, arg2);
+    fputs(buf, stdout);
+    if (size != STRING_SIZE) {
+        ++failures;
+        printf("snprintf(sizeof buf) gave the wrong size:\n %d.\n", size);
+    }
+
+    /* Does snprintf() return the full-formatted size even when the buffer
+    ** is short?  Does it write beyond the end of that buffer?
+    */
+
+    fillbuf();
+    size = snprintf(buf, STRING_SIZE - 5u, format, arg1, arg2);
+    if (size != STRING_SIZE) {
+        ++failures;
+        printf("snprintf(STRING_SIZE-5) gave the wrong size:\n %d.\n", size);
+    }
+    if (buf[STRING_SIZE - 5u - 1u] != '\0' || buf[STRING_SIZE - 5u] != 0xFF) {
+        ++failures;
+        printf("snprintf(STRING_SIZE-5) wrote beyond\n the end of the buffer.\n");
+    }
+
+    /* Does snprintf() detect a buffer size that is too big? */
+
+    fillbuf();
+    errno = 0;
+    size = snprintf(buf, 0x8000, format, arg1, arg2);
+    if (size >= 0) {
+        ++failures;
+        printf("snprintf(0x8000) didn't give an error:\n %d; errno=%d.\n", size, errno);
+    } else {
+        printf("snprintf(0x8000) did give an error:\n errno=%d.\n", errno);
+    }
+    if (buf[0] != 0xFF) {
+        ++failures;
+        printf("snprintf(0x8000) wrote into the buffer.\n");
+    }
+
+    /* snprintf() must measure the length of the formatted output even when the
+    ** buffer size is zero.  But, it must not touch the buffer.
+    */
+
+    fillbuf();
+    size = snprintf(buf, 0, format, arg1, arg2);
+    if (size != STRING_SIZE) {
+        ++failures;
+        printf("snprintf(0) gave the wrong size:\n %d.\n", size);
+    }
+    if (buf[0] != 0xFF) {
+        ++failures;
+        printf("snprintf(0) wrote into the buffer.\n");
+    }
+
+    /* Does sprintf() detect a zero buffer-pointer? */
+
+    errno = 0;
+    size = sprintf(NULL, format, arg1, arg2);
+    if (size >= 0) {
+        ++failures;
+        printf("sprintf(NULL) didn't give an error:\n %d; errno=%d.\n", size, errno);
+    } else {
+        printf("sprintf(NULL) did give an error:\n errno=%d.\n", errno);
+    }
+
+    /* snprintf() must measure the length of the formatted output even when the
+    ** buffer size is zero.  A zero pointer is not an error, in that case.
+    */
+
+    size = snprintf(NULL, 0, format, arg1, arg2);
+    if (size != STRING_SIZE) {
+        ++failures;
+        printf("snprintf(NULL,0) gave the wrong size:\n %d.\n", size);
+    }
+
+    if (failures != 0) {
+        printf("There were %u", failures);
+    } else {
+        printf("There were no");
+    }
+    printf(" failures.\nTap a key. ");
+    cgetc();
+
+    return failures;
+}