Initial commit

5 files changed, 274 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..fb3b258
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.o
+c-style
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..bd0942d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,10 @@
+CC=c99
+CFLAGS=-Wall -Wextra -Wunreachable-code -ftrapv -D_POSIX_C_SOURCE=2
+
+all: c-style
+
+c-style: style.o
+	$(CC) -o c-style $?
+
+clean:
+	rm -f *.o
diff --git a/README b/README
new file mode 100644
index 0000000..577ad57
--- /dev/null
+++ b/README
@@ -0,0 +1,30 @@
+Delwink Style
+=============
+
+This repository contains documentation for Delwink's coding conventions. The
+Makefile contains build instructions for all compiled language examples.
+
+Standards
+---------
+
+C code should be restricted to no later a standard than C99, and Makefiles
+should be POSIX-compliant. On GNU systems, use bmake (NetBSD make) to test
+Makefile compatibility.
+
+Shell scripts should be strictly Bourne-compatible, using `#!/bin/sh` at the
+top of the file. Use tabs for indentation, and don't go over 80 columns.
+
+Goal
+----
+
+Delwink strives for cross-compatibility of its software. In compiled languages
+especially, strict adherence to cross-platform standards is key. In addition to
+compatibility of software, we want compatibility between environments as
+well. Our code conventions aim to make it easier to edit source with any editor
+without relying on extensions.
+
+Errors
+------
+
+If you notice a compatibility error, please report it (preferably with a
+solution) to Delwink so that we may update it immediately.
diff --git a/README.md b/README.md
new file mode 120000
index 0000000..100b938
--- /dev/null
+++ b/README.md
@@ -0,0 +1 @@
+README
\ No newline at end of file
diff --git a/style.c b/style.c
new file mode 100644
index 0000000..880670e
--- /dev/null
+++ b/style.c
@@ -0,0 +1,231 @@
+/*
+ *  style.c - Delwink C coding conventions demo
+ *  Copyright (C) 2017 Delwink, LLC
+ *
+ *  Copying and distribution of this file, with or without modification,
+ *  are permitted in any medium without royalty provided the copyright
+ *  notice and this notice are preserved.  This file is offered as-is,
+ *  without any warranty.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/*
+ * All source files should have an appropriate license header such as the one
+ * above. Multi-line comments look like this.
+ */
+
+/* Single-line comments look like this when using C89. */
+
+// Single-line comments look like this when using C99 or later.
+
+#define PROGNAME "c-style"
+#define VERSION "20170512"
+#define USAGE PROGNAME " v" VERSION "\n"				\
+	"Prints Fibonacci sequences\n"					\
+	"USAGE: " PROGNAME " [-h] [-v] [-s START] [-e END] [-o FILE]\n" \
+	"\n"								\
+	"OPTIONS:\n"							\
+	"\t-h:\tShows this help and exits.\n"				\
+	"\n"								\
+	"\t-v:\tShows version info and exits.\n"			\
+	"\n"								\
+	"\t-s START:\tStarts sequence at START.\n"			\
+	"\n"								\
+	"\t-e END:\tEnds sequence at END.\n"				\
+	"\n"								\
+	"\t-o FILE:\tSaves output in FILE.\n"
+
+// Doc comments are doxygen-compliant. See below.
+
+/**
+ * @brief Data structure to hold the state of a Fibonacci sequence.
+ */
+struct fib_state_machine
+{ // opening brace always goes on next line
+	unsigned int value; // struct members are always on separate lines,
+	unsigned int next_value; // even when the same type and adjacent.
+	unsigned int index;
+}; // don't use typedefs unless you're trying to hide something.
+
+// note: doc comments usually go in headers
+
+/**
+ * @brief Initializes a Fibonacci state machine.
+ * @param self The machine to be initialized.
+ */
+static void // function return types stay on their own line, even in headers
+fib_init(struct fib_state_machine *self)
+{
+	/*
+	 * Indentation is one tab character everywhere. Don't let lines go
+	 * longer than 80 columns. Tabs count as 8 columns.
+	 */
+
+	self->value = 0;
+	self->next_value = 1;
+	self->index = 0;
+}
+
+/**
+ * @brief Advances a Fibonacci sequence to its next value.
+ * @param self The state of the sequence.
+ */
+static void
+fib_advance(struct fib_state_machine *self)
+{
+	unsigned int temp = self->value + self->next_value;
+
+	self->value = self->next_value;
+	self->next_value = temp;
+	++self->index; // use prefix when only incrementing/decrementing
+}
+
+/**
+ * @brief Prints a Fibonacci sequence.
+ * @param start The starting index.
+ * @param end The ending index (exclusive).
+ * @param fmt The print format (MUST contain only one %u for insertion).
+ * @param dest The destination of the printed sequence.
+ */
+static void
+print_sequence(unsigned int start, unsigned int end,
+	/*
+	 * On long parameter lists, indent like so. Use `const` qualifier when
+	 * appropriate.
+	 */
+	const char *fmt, FILE *dest)
+{
+	if (end <= start)
+		return; // fail quickly
+
+	if (!fmt) // fine to use ! to check for NULL pointer values
+		fmt = "%u\n"; // no braces needed on single statement
+
+	if (!dest)
+		dest = stdout;
+
+	/*
+	 * Create variables where it's appropriate. Don't constrain yourself
+	 * to putting them at the top of functions, unless using C89.
+	 *
+	 * Also, let the compiler handle memory allocation when you don't need
+	 * dynamic allocation and you're not taking up a lot of space. Use
+	 * your own judgment for determining this, but stacks are pretty big
+	 * on modern hardware.
+	 */
+	struct fib_state_machine fib;
+	fib_init(&fib);
+
+	while (fib.index < start)
+		fib_advance(&fib);
+
+	do
+	{
+		fprintf(dest, fmt, fib.value);
+		fib_advance(&fib);
+	} while (fib.index < end);
+}
+
+/**
+ * @brief Prints usage info and exits.
+ * @param rc Exit code to be used.
+ */
+static void
+usage(int rc)
+{
+	fprintf(stderr, USAGE);
+	exit(rc);
+}
+
+/**
+ * @brief Converts a string to an index or fails.
+ * @param src The source string to be converted.
+ * @param lower The lower bound of the index.
+ * @param upper The upper bound of the index (inclusive).
+ * @param arg The argument for this index.
+ * @return The specified index, if it was valid.
+ */
+static unsigned int
+str_to_index(const char *src, int lower, int upper, int arg)
+{
+	int temp;
+
+	int rc = sscanf(src, "%d", &temp);
+	if (rc != 1)
+	{
+		fprintf(stderr, "Argument to -%c must be a number\n", arg);
+		exit(1);
+	}
+
+	if (temp < lower || temp > upper)
+	{
+		// don't chop string literals that go over 80 columns
+		fprintf(stderr,
+			PROGNAME ": argument to -%c must be between %d and %d\n",
+			arg, lower, upper);
+		exit(1);
+	}
+
+	return (unsigned int) temp;
+}
+
+int // main ALWAYS returns int
+main(int argc, char *argv[])
+{
+	FILE *outfile = stdout;
+	int c;
+	unsigned int start = 0, end = 10;
+
+	// use POSIX getopt
+	while ((c = getopt(argc, argv, ":e:ho:s:v")) != -1)
+	{
+		switch (c)
+		{
+		case 'e':
+			end = str_to_index(optarg, 0, 48, c);
+			break;
+
+		case 'h':
+			usage(0);
+
+		case 'o':
+			outfile = fopen(optarg, "w");
+			if (!outfile)
+			{
+				fprintf(stderr,
+					PROGNAME ": could not open %s: %s\n",
+					optarg, strerror(errno));
+				return 1;
+			}
+			break;
+
+		case 's':
+			start = str_to_index(optarg, 0, 48, c);
+			break;
+
+		case 'v':
+			fprintf(stderr, PROGNAME " v" VERSION "\n");
+			return 0;
+
+		case ':':
+			fprintf(stderr,
+				PROGNAME ": option %c requires an argument\n",
+				optopt);
+			// SPILLS OVER!
+		case '?':
+			usage(1);
+		}
+	}
+
+	print_sequence(start, end, NULL, outfile);
+
+	if (outfile != stdout)
+		fclose(outfile);
+
+	return 0;
+}