Initial Spring 2016 commit.

common/libc/printf/snprintf.c

@@ -0,0 +1,157 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * This file is shared between libc and the kernel, so don't put anything
+ * in here that won't work in both contexts.
+ */
+
+#ifdef _KERNEL
+#include <types.h>
+#include <lib.h>
+
+#else
+#include <stdio.h>
+
+#endif /* _KERNEL */
+
+#include <stdarg.h>
+
+/*
+ * Standard C string/IO function: printf into a character buffer.
+ */
+
+
+/*
+ * Context structure for snprintf: buffer to print into, maximum
+ * length, and index of the next character to write.
+ *
+ * Note that while the length argument to snprintf includes space for
+ * a null terminator, SNP.buflen does not. This is to make something
+ * vaguely reasonable happen if a length of 0 is passed to snprintf.
+ */
+
+typedef struct {
+	char *buf;
+	size_t buflen;
+	size_t bufpos;
+} SNP;
+
+/*
+ * Send function for snprintf. This is the function handed to the
+ * printf guts. It gets called with mydata pointing to the context,
+ * and some string data of length LEN in DATA. DATA is not necessarily
+ * null-terminated.
+ */
+
+static
+void
+__snprintf_send(void *mydata, const char *data, size_t len)
+{
+	SNP *snp = mydata;
+	unsigned i;
+
+	/* For each character we're sent... */
+	for (i=0; i<len; i++) {
+
+		/* If we aren't past the length, */
+		if (snp->bufpos < snp->buflen) {
+
+			/* store the character */
+			snp->buf[snp->bufpos] = data[i];
+
+			/* and increment the position. */
+			snp->bufpos++;
+		}
+	}
+}
+
+/*
+ * The va_list version of snprintf.
+ */
+int
+vsnprintf(char *buf, size_t len, const char *fmt, va_list ap)
+{
+	int chars;
+	SNP snp;
+
+	/*
+	 * Fill in the context structure.
+	 * We set snp.buflen to the number of characters that can be
+	 * written (excluding the null terminator) so as not to have
+	 * to special-case the possibility that we got passed a length
+	 * of zero elsewhere.
+	 */
+	snp.buf = buf;
+	if (len==0) {
+		snp.buflen = 0;
+	}
+	else {
+		snp.buflen = len-1;
+	}
+	snp.bufpos = 0;
+
+	/* Call __vprintf to do the actual work. */
+	chars = __vprintf(__snprintf_send, &snp, fmt, ap);
+
+	/*
+	 * Add a null terminator. If the length *we were passed* is greater
+	 * than zero, we reserved a space in the buffer for the terminator,
+	 * so this won't overflow. If the length we were passed is zero,
+	 * nothing will have been or should be written anyway, and buf
+	 * might even be NULL. (C99 explicitly endorses this possibility.)
+	 */
+	if (len > 0) {
+		buf[snp.bufpos] = 0;
+	}
+
+	/*
+	 * Return the number of characters __vprintf processed.
+	 * According to C99, snprintf should return this number, not
+	 * the number of characters actually stored, and should not
+	 * return -1 on overflow but only on other errors. (All none
+	 * of them since we don't do multibyte characters...)
+	 */
+	return chars;
+}
+
+/*
+ * snprintf - hand off to vsnprintf.
+ */
+int
+snprintf(char *buf, size_t len, const char *fmt, ...)
+{
+	int chars;
+	va_list ap;
+	va_start(ap, fmt);
+	chars = vsnprintf(buf, len, fmt, ap);
+	va_end(ap);
+	return chars;
+}
+