7 files changed, 404 insertions, 0 deletions
diff --git a/src/build.c b/src/build.c
new file mode 100644
index 0000000..764ec2b
--- /dev/null
+++ b/src/build.c
@@ -0,0 +1,262 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <stdbool.h>
+#include <assert.h>
+
+#include <libgen.h> /* dirname(), basename() */
+
+#include "build.h"
+#include "util.h"
+#define __FILENAME__ "build.c"
+#include "dbg.h"
+
+/* TODO: more useful return codes? */
+
+const char do_file_ext[] = ".do";
+const char default_name[] = "default";
+const char temp_ext[] = ".redoing.tmp";
+
+int build_target(const char *target) {
+	assert(target);
+
+	int retval = 0;
+	printf("redo  %s\n", target);
+
+	/* get the do-file which we are going to execute */
+	char *do_file = get_do_file(target);
+	if (do_file == NULL) {
+		if (file_exists(target)) {
+			/* if our target file has no do file associated but exists,
+			   then we treat it as a source */
+			/* TODO: write dependencies */
+			goto exit;
+		}
+		fprintf(stderr, "%s couldn't be built because no "
+				"suitable do-file exists\n", target);
+		retval = 1;
+		goto exit;
+	}
+
+	debug("Using do-file %s\n", do_file);
+
+	char *temp_output = concat(2, target, temp_ext);
+
+    pid_t pid = fork();
+    if (pid == -1) {
+        /* failure */
+		fatal("redo: failed to fork() new process");
+    } else if (pid == 0) {
+        /* child */
+
+		/* change directory to our target */
+		char *dirc = ec_strdup(target);
+		char *dtarget = dirname(dirc);
+		if (chdir(dtarget) == -1)
+			fatal("redo: failed to change directory to %s", dtarget);
+
+		free(dirc);
+
+		/* target is now in the cwd so change path accordingly */
+		char *btarget = xbasename(target);
+		char *bdo_file = xbasename(do_file);
+
+		/* read and parse shebang */
+		FILE *fp = fopen(bdo_file, "rb+");
+		if (!fp)
+			fatal("redo: failed to open %s", bdo_file);
+
+		const size_t bufsize = 1024;
+		char buf[bufsize];
+
+		buf[ fread(buf, 1, sizeof(buf)-1, fp) ] = '\0';
+		if (ferror(fp))
+			fatal("redo: failed to read from %s", bdo_file);
+
+		fclose(fp);
+
+		char **argv;
+		size_t i = 0;
+		if (buf[0] == '#' && buf[1] == '!') {
+			argv = parsecmd(&buf[2], &i, 5);
+		} else {
+			argv = ec_malloc(7 * sizeof(char*));
+			argv[i++] = "/bin/sh";
+			argv[i++] = "-e";
+		}
+
+		argv[i++] = bdo_file;
+		argv[i++] = (char*) btarget;
+		char *basename = remove_ext(btarget);
+		argv[i++] = basename;
+		argv[i++] = temp_output;
+		argv[i] = NULL;
+
+		execv(argv[0], argv);
+
+		/* execv should never return */
+		fatal("redo: failed to replace the child process with %s", argv[0]);
+	}
+
+    /* parent */
+    int returncode;
+    waitpid(pid, &returncode, 0);
+	bool remove_temp = true;
+
+    if (WIFEXITED(returncode)) {
+        if (0 != returncode) {
+			fprintf(stderr, "redo: invoked do-file %s failed with %d\n",
+					do_file, WEXITSTATUS(returncode));
+        } else {
+			/* successfull */
+
+            /* if the file is 0 bytes long we delete it */
+			off_t f_size = fsize(temp_output);
+			if (f_size == -1) {
+				if (errno != ENOENT)
+					fatal("redo: failed to determine the size of %s", temp_output);
+            } else if (f_size)
+                remove_temp = false;
+        }
+    } else {
+        /* something very wrong happened with the child */
+		fprintf(stderr, "redo: invoked do-file did not terminate correctly\n");
+    }
+
+    if (remove_temp) {
+	    if (remove(temp_output))
+            if (errno != ENOENT)
+		        fatal("redo: failed to remove %s", temp_output);
+    } else {
+	    if (rename(temp_output, target))
+		    fatal("redo: failed to rename %s to %s", temp_output, target);
+    }
+
+	free(temp_output);
+ exit:
+	free(do_file);
+
+	return retval;
+}
+
+/* Returns the right do-file for target */
+char *get_do_file(const char *target) {
+	assert(target);
+	/* target + ".do" */
+	char *temp = concat(2, target, do_file_ext);
+	if (file_exists(temp))
+		return temp;
+	free(temp);
+
+	/* default + get_extension(target) + ".do" */
+	temp = concat(3, default_name, take_extension(target), do_file_ext);
+	if (file_exists(temp))
+		return temp;
+	free(temp);
+
+	/* Redofile */
+	temp = strdup("Redofile");
+	if (file_exists(temp))
+		return temp;
+	free(temp);
+
+	return NULL;
+}
+
+/* Returns the extension of the target or the empty string if none was found */
+char *take_extension(const char *target) {
+	assert(target);
+	char *temp = strrchr(target, '.');
+	if (temp)
+		return temp;
+	else {
+		return "";
+	}
+}
+
+/* Checks if target exists and prints a debug message if access() failed
+   except if it failed with ENOENT. */
+bool file_exists(const char *target) {
+	assert(target);
+	if (!access(target, F_OK))
+		return true;
+	if (errno != ENOENT)
+		debug("Failed to access %s: %s\n", target, strerror(errno));
+	return false;
+}
+
+/* Returns a new copy of str with the extension removed, where the extension is
+   everything behind the last dot, including the dot. */
+char *remove_ext(const char *str) {
+	assert(str);
+	size_t len;
+	char *ret, *dot = NULL;
+
+	for (len = 0; str[len]; ++len)
+		if (str[len] == '.')
+			dot = (char*) &str[len];
+
+	if (dot) /* recalculate length to only reach just before the last dot */
+		len = dot - str;
+
+	ret = ec_malloc(len+1);
+	memcpy(ret, str, len);
+	ret[len] = '\0';
+
+	return ret;
+}
+
+/* Breaks cmd at spaces and stores a pointer to each argument in the returned
+   array. The index i is incremented to point to the next free pointer. The
+   returned array is guaranteed to have at least keep_free entries left */
+char **parsecmd(char *cmd, size_t *i, size_t keep_free) {
+	assert(cmd);
+	size_t argv_len = 16;
+	char **argv = ec_malloc(argv_len * sizeof(char*));
+	size_t j = 0;
+	bool prev_space = true;
+	for (;; ++j) {
+		switch (cmd[j]) {
+		case ' ':
+			cmd[j] = '\0';
+			prev_space = true;
+			break;
+		case '\n':
+		case '\r':
+			cmd[j] = '\0';
+		case '\0':
+			return argv;
+		default:
+			if (!prev_space)
+				break;
+			/* check if we have enough space */
+			while (*i+keep_free >= argv_len) {
+				argv_len *= 2;
+				debug("Reallocating memory (now %zu)\n", argv_len);
+				/* TODO: replace realloc? */
+				char **new_ptr = realloc(argv, argv_len * sizeof(char*));
+				if (!new_ptr)
+					fatal("redo: couldn't realloc %zu bytes",
+						  argv_len * sizeof(char*));
+				argv = new_ptr;
+			}
+
+			prev_space = false;
+			argv[*i] = &cmd[j];
+			++*i;
+		}
+	}
+}
+
+/* Returns the size of fn */
+off_t fsize(const char *fn) {
+    struct stat st;
+
+    if (stat(fn, &st))
+		return -1;
+
+	return st.st_size;
+}
diff --git a/src/build.h b/src/build.h
new file mode 100644
index 0000000..418f4b0
--- /dev/null
+++ b/src/build.h
@@ -0,0 +1,16 @@
+#ifndef __RBUILD_H__
+#define __RBUILD_H__
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <sys/types.h>
+
+extern char *get_do_file(const char *target);
+extern int build_target(const char *target);
+extern bool file_exists(const char *target);
+extern char *take_extension(const char *target);
+extern char *remove_ext(const char *str);
+extern char **parsecmd(char *cmd, size_t *i, size_t keep_free);
+extern off_t fsize(const char *fn);
+
+#endif
diff --git a/src/dbg.h b/src/dbg.h
new file mode 100644
index 0000000..014c358
--- /dev/null
+++ b/src/dbg.h
@@ -0,0 +1,28 @@
+#ifndef __DBG_H__
+#define __DBG_H__
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+// #define __BFILE__ (strrchr(__FILE__, '/') ? strrchr(__FILE__, '/') + 1 : __FILE__)
+#ifndef __FILENAME__
+#define __FILENAME__ __FILE__
+#endif
+
+/* helper functions which help in replacing the GNU extension ##__VA_ARGS__ */
+#define STRINGIFY(x) #x
+#define LOG_HELPER(f,l,...) fprintf(stderr, "("f":"STRINGIFY(l)"): "__VA_ARGS__)
+#define FATAL_HELPER(M, ...) log_err(M ": %s\n", __VA_ARGS__)
+
+#ifdef NDEBUG
+#define debug(...)
+#else
+#define debug(...) log_err(__VA_ARGS__)
+#endif
+
+#define log_err(...) LOG_HELPER(__FILENAME__, __LINE__, __VA_ARGS__)
+#define fatal(...) {FATAL_HELPER(__VA_ARGS__, strerror(errno)); exit(EXIT_FAILURE);}
+
+#endif
diff --git a/src/redo-ifchange.c b/src/redo-ifchange.c
new file mode 100644
index 0000000..9415776
--- /dev/null
+++ b/src/redo-ifchange.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+
+#include "build.h"
+
+int main(int argc, char *argv[]) {
+	int i;
+	for (i = 1; i < argc; ++i) {
+		build_target(argv[i]);
+	}
+}
diff --git a/src/redo.c b/src/redo.c
new file mode 100644
index 0000000..c745c54
--- /dev/null
+++ b/src/redo.c
@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+#include "build.h"
+#include "util.h"
+
+int main(int argc, char *argv[]) {
+	if (argc < 2) {
+		build_target("all");
+	} else {
+		int i;
+		for (i = 1; i < argc; ++i) {
+			build_target(argv[i]);
+		}
+	}
+}
diff --git a/src/util.c b/src/util.c
new file mode 100644
index 0000000..e67ec18
--- /dev/null
+++ b/src/util.c
@@ -0,0 +1,60 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdarg.h>
+#include <assert.h>
+
+#include "util.h"
+#define __FILENAME__ "util.c"
+#include "dbg.h"
+
+#include "../config.h"
+
+/* A safe malloc wrapper. */
+void *ec_malloc(size_t size) {
+    void *ptr = malloc(size);
+    if(ptr == NULL)
+		fatal("redo: cannot allocate %zu bytes", size);
+	
+    return ptr;
+}
+
+/* For concating multiple strings into a single larger one. */
+char *concat(size_t count, ...) {
+	assert(count > 0);
+	va_list ap, ap2;
+	va_start(ap, count);
+	va_copy(ap2, ap);
+	size_t i, size = 0, args_len[count];
+	for (i = 0; i < count; ++i) {
+		args_len[i] = strlen(va_arg(ap, char*));
+		size += args_len[i];
+	}
+	size++;
+	char *result = ec_malloc(size);
+	/* debug("Allocated %zu bytes at %p\n", size, result); */
+	uintptr_t offset = 0;
+	for (i = 0; i < count; ++i) {
+		strcpy(&result[offset], va_arg(ap2, char*));
+		offset += args_len[i];
+	}
+	va_end(ap);
+	va_end(ap2);
+	return result;
+}
+
+char *xbasename(const char *path) {
+	assert(path);
+	char *ptr = strrchr(path, '/');
+	return ptr? ptr+1 : (char*) path;
+}
+
+char *ec_strdup(const char* str) {
+	assert(str);
+	size_t len = strlen(str) + 1;
+	char *ptr = malloc(len);
+	if (!ptr)
+		fatal("redo: failed to duplicate string");
+
+	return memcpy(ptr, str, len);;
+}
diff --git a/src/util.h b/src/util.h
new file mode 100644
index 0000000..40780d8
--- /dev/null
+++ b/src/util.h
@@ -0,0 +1,13 @@
+#ifndef __RUTIL_H__
+#define __RUTIL_H__
+
+#include <stdlib.h>
+#include "../config.h"
+
+extern char *concat(size_t count, ...);
+extern void *ec_malloc(size_t size);
+extern char *ec_strdup(const char* str);
+extern char *strdup(const char *str);
+extern char *xbasename(const char *path);
+
+#endif