1 files changed, 133 insertions, 0 deletions
diff --git a/lib/sprint.c b/lib/sprint.c
new file mode 100644
index 0000000..d2e0a7e
--- /dev/null
+++ b/lib/sprint.c
@@ -0,0 +1,133 @@
+/**
+** @file	sprint.c
+**
+** @author	Numerous CSCI-452 classes
+**
+** @brief	C implementations of common library functions
+*/
+
+#ifndef SPRINT_SRC_INC
+#define SPRINT_SRC_INC
+
+#include <common.h>
+
+#include <lib.h>
+
+/**
+** sprint(dst,fmt,...) - formatted output into a string buffer
+**
+** @param dst The string buffer
+** @param fmt Format string
+**
+** The format string parameter is followed by zero or more additional
+** parameters which are interpreted according to the format string.
+**
+** NOTE:  assumes the buffer is large enough to hold the result string
+**
+** NOTE:  relies heavily on the x86 parameter passing convention
+** (parameters are pushed onto the stack in reverse order as
+** 32-bit values).
+*/
+void sprint( char *dst, char *fmt, ... ) {
+	int32_t *ap;
+	char buf[ 12 ];
+	char ch;
+	char *str;
+	int leftadjust;
+	int width;
+	int len;
+	int padchar;
+
+	/*
+	** Get characters from the format string and process them
+	**
+	** We use the "old-school" method of handling variable numbers
+	** of parameters.  We assume that parameters are passed on the
+	** runtime stack in consecutive longwords; thus, if the first
+	** parameter is at location 'x', the second is at 'x+4', the
+	** third at 'x+8', etc.  We use a pointer to a 32-bit thing
+	** to point to the next "thing", and interpret it according
+	** to the format string.
+	*/
+	
+	// get the pointer to the first "value" parameter
+	ap = (int *)(&fmt) + 1;
+
+	// iterate through the format string
+	while( (ch = *fmt++) != '\0' ){
+		/*
+		** Is it the start of a format code?
+		*/
+		if( ch == '%' ){
+			/*
+			** Yes, get the padding and width options (if there).
+			** Alignment must come at the beginning, then fill,
+			** then width.
+			*/
+			leftadjust = 0;
+			padchar = ' ';
+			width = 0;
+			ch = *fmt++;
+			if( ch == '-' ){
+				leftadjust = 1;
+				ch = *fmt++;
+			}
+			if( ch == '0' ){
+				padchar = '0';
+				ch = *fmt++;
+			}
+			while( ch >= '0' && ch <= '9' ){
+				width *= 10;
+				width += ch - '0';
+				ch = *fmt++;
+			}
+
+			/*
+			** What data type do we have?
+			*/
+			switch( ch ) {
+
+			case 'c':  // characters are passed as 32-bit values
+				ch = *ap++;
+				buf[ 0 ] = ch;
+				buf[ 1 ] = '\0';
+				dst = padstr( dst, buf, 1, width, leftadjust, padchar );
+				break;
+
+			case 'd':
+				len = cvtdec( buf, *ap++ );
+				dst = padstr( dst, buf, len, width, leftadjust, padchar );
+				break;
+
+			case 's':
+				str = (char *) (*ap++);
+				dst = padstr( dst, str, -1, width, leftadjust, padchar );
+				break;
+
+			case 'x':
+				len = cvthex( buf, *ap++ );
+				dst = padstr( dst, buf, len, width, leftadjust, padchar );
+				break;
+
+			case 'o':
+				len = cvtoct( buf, *ap++ );
+				dst = padstr( dst, buf, len, width, leftadjust, padchar );
+				break;
+
+			case 'u':
+				len = cvtuns( buf, *ap++ );
+				dst = padstr( dst, buf, len, width, leftadjust, padchar );
+				break;
+
+			}
+		} else {
+			// no, it's just an ordinary character
+			*dst++ = ch;
+		}
+	}
+
+	// NUL-terminate the result
+	*dst = '\0';
+}
+
+#endif