/*
   * "Optimize" a list of dependencies as spit out by gcc -MD
   * for the kernel build
   * ===========================================================================
   *
   * Author       Kai Germaschewski
   * Copyright    2002 by Kai Germaschewski  <kai.germaschewski@gmx.de>
   *
   * This software may be used and distributed according to the terms
   * of the GNU General Public License, incorporated herein by reference.
   *
   *
   * Introduction:
   *
   * gcc produces a very nice and correct list of dependencies which
   * tells make when to remake a file.
   *
   * To use this list as-is however has the drawback that virtually

   * every file in the kernel includes autoconf.h.

   *

   * If the user re-runs make *config, autoconf.h will be

   * regenerated.  make notices that and will rebuild every file which
   * includes autoconf.h, i.e. basically all files. This is extremely
   * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
   *
   * So we play the same trick that "mkdep" played before. We replace

   * the dependency on autoconf.h by a dependency on every config

   * option which is mentioned in any of the listed prerequisites.

   *

   * kconfig populates a tree in include/config/ with an empty file
   * for each config symbol and when the configuration is updated
   * the files representing changed config options are touched
   * which then let make pick up the changes and the files that use
   * the config symbols are rebuilt.

   *
   * So if the user changes his CONFIG_HIS_DRIVER option, only the objects

   * which depend on "include/config/his/driver.h" will be rebuilt,

   * so most likely only his driver ;-)
   *
   * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
   *
   * So to get dependencies right, there are two issues:
   * o if any of the files the compiler read changed, we need to rebuild
   * o if the command line given to the compile the file changed, we
   *   better rebuild as well.
   *
   * The former is handled by using the -MD output, the later by saving
   * the command line used to compile the old object and comparing it
   * to the one we would now use.
   *
   * Again, also this idea is pretty old and has been discussed on
   * kbuild-devel a long time ago. I don't have a sensibly working
   * internet connection right now, so I rather don't mention names
   * without double checking.
   *
   * This code here has been based partially based on mkdep.c, which
   * says the following about its history:
   *
   *   Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
   *   This is a C version of syncdep.pl by Werner Almesberger.
   *
   *
   * It is invoked as
   *
   *   fixdep <depfile> <target> <cmdline>
   *
   * and will read the dependency file <depfile>
   *
   * The transformed dependency snipped is written to stdout.
   *
   * It first generates a line
   *
   *   cmd_<target> = <cmdline>
   *
   * and then basically copies the .<target>.d file to stdout, in the

   * process filtering out the dependency on autoconf.h and adding

   * dependencies on include/config/my/option.h for every

   * CONFIG_MY_OPTION encountered in any of the prerequisites.

   *

   * We don't even try to really parse the header files, but

   * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
   * be picked up as well. It's not a problem with respect to
   * correctness, since that can only give too many dependencies, thus
   * we cannot miss a rebuild. Since people tend to not mention totally
   * unrelated CONFIG_ options all over the place, it's not an
   * efficiency problem either.
   *
   * (Note: it'd be easy to port over the complete mkdep state machine,
   *  but I don't think the added complexity is worth it)
   */

  
  #include <sys/types.h>
  #include <sys/stat.h>

  #include <unistd.h>
  #include <fcntl.h>
  #include <string.h>

  #include <stdarg.h>

  #include <stdlib.h>
  #include <stdio.h>

  #include <ctype.h>

  static void usage(void)

  {

  	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>
  ");

  	exit(1);
  }

  /*

   * In the intended usage of this program, the stdout is redirected to .*.cmd
   * files. The return value of printf() and putchar() must be checked to catch
   * any error, e.g. "No space left on device".
   */
  static void xprintf(const char *format, ...)
  {
  	va_list ap;
  	int ret;
  
  	va_start(ap, format);
  	ret = vprintf(format, ap);
  	if (ret < 0) {
  		perror("fixdep");
  		exit(1);
  	}
  	va_end(ap);
  }
  
  static void xputchar(int c)
  {
  	int ret;
  
  	ret = putchar(c);
  	if (ret == EOF) {
  		perror("fixdep");
  		exit(1);
  	}
  }
  
  /*

   * Print out a dependency path from a symbol name
   */

  static void print_dep(const char *m, int slen, const char *dir)

  {

  	int c, prev_c = '/', i;

  	xprintf("    $(wildcard %s/", dir);

  	for (i = 0; i < slen; i++) {
  		c = m[i];
  		if (c == '_')
  			c = '/';
  		else
  			c = tolower(c);

  		if (c != '/' || prev_c != '/')

  			xputchar(c);

  		prev_c = c;

  	}

  	xprintf(".h) \\
  ");

  }

  struct item {
  	struct item	*next;
  	unsigned int	len;
  	unsigned int	hash;

  	char		name[];

  };

  #define HASHSZ 256
  static struct item *hashtab[HASHSZ];

  static unsigned int strhash(const char *str, unsigned int sz)
  {
  	/* fnv32 hash */
  	unsigned int i, hash = 2166136261U;

  	for (i = 0; i < sz; i++)
  		hash = (hash ^ str[i]) * 0x01000193;
  	return hash;
  }

  
  /*
   * Lookup a value in the configuration string.
   */

  static int is_defined_config(const char *name, int len, unsigned int hash)

  {

  	struct item *aux;
  
  	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
  		if (aux->hash == hash && aux->len == len &&
  		    memcmp(aux->name, name, len) == 0)

  			return 1;
  	}
  	return 0;
  }
  
  /*
   * Add a new value to the configuration string.
   */

  static void define_config(const char *name, int len, unsigned int hash)

  {

  	struct item *aux = malloc(sizeof(*aux) + len);

  	if (!aux) {
  		perror("fixdep:malloc");
  		exit(1);
  	}
  	memcpy(aux->name, name, len);
  	aux->len = len;
  	aux->hash = hash;
  	aux->next = hashtab[hash % HASHSZ];
  	hashtab[hash % HASHSZ] = aux;

  }
  
  /*

   * Record the use of a CONFIG_* word.
   */

  static void use_config(const char *m, int slen)

  {

  	unsigned int hash = strhash(m, slen);

  	if (is_defined_config(m, slen, hash))

  	    return;

  	define_config(m, slen, hash);

  	print_dep(m, slen, "include/config");

  }

  /* test if s ends in sub */
  static int str_ends_with(const char *s, int slen, const char *sub)
  {
  	int sublen = strlen(sub);
  
  	if (sublen > slen)
  		return 0;
  
  	return !memcmp(s + slen - sublen, sub, sublen);
  }

  static void parse_config_file(const char *p)

  {

  	const char *q, *r;

  	const char *start = p;

  
  	while ((p = strstr(p, "CONFIG_"))) {

  		if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
  			p += 7;
  			continue;
  		}

  		p += 7;

  		q = p;

  		while (isalnum(*q) || *q == '_')

  			q++;

  		if (str_ends_with(p, q - p, "_MODULE"))

  			r = q - 7;
  		else
  			r = q;
  		if (r > p)
  			use_config(p, r - p);
  		p = q;

  	}
  }

  static void *read_file(const char *filename)

  {
  	struct stat st;
  	int fd;

  	char *buf;

  
  	fd = open(filename, O_RDONLY);
  	if (fd < 0) {

  		fprintf(stderr, "fixdep: error opening file: ");

  		perror(filename);
  		exit(2);
  	}

  	if (fstat(fd, &st) < 0) {

  		fprintf(stderr, "fixdep: error fstat'ing file: ");

  		perror(filename);
  		exit(2);
  	}

  	buf = malloc(st.st_size + 1);
  	if (!buf) {

  		perror("fixdep: malloc");

  		exit(2);

  	}

  	if (read(fd, buf, st.st_size) != st.st_size) {

  		perror("fixdep: read");

  		exit(2);

  	}

  	buf[st.st_size] = '\0';

  	close(fd);

  	return buf;

  }

  /* Ignore certain dependencies */
  static int is_ignored_file(const char *s, int len)
  {
  	return str_ends_with(s, len, "include/generated/autoconf.h") ||

  	       str_ends_with(s, len, "include/generated/autoksyms.h");

  }

  /*
   * Important: The below generated source_foo.o and deps_foo.o variable
   * assignments are parsed not only by make, but also by the rather simple
   * parser in scripts/mod/sumversion.c.
   */

  static void parse_dep_file(char *m, const char *target)

  {

  	char *p;

  	int is_last, is_target;

  	int saw_any_target = 0;
  	int is_first_dep = 0;

  	void *buf;

  	while (1) {

  		/* Skip any "white space" */

  		while (*m == ' ' || *m == '\\' || *m == '
  ')

  			m++;

  
  		if (!*m)
  			break;

  		/* Find next "white space" */

  		p = m;

  		while (*p && *p != ' ' && *p != '\\' && *p != '
  ')

  			p++;

  		is_last = (*p == '\0');

  		/* Is the token we found a target name? */
  		is_target = (*(p-1) == ':');
  		/* Don't write any target names into the dependency file */
  		if (is_target) {
  			/* The /next/ file is the first dependency */
  			is_first_dep = 1;

  		} else if (!is_ignored_file(m, p - m)) {

  			*p = '\0';

  			/*
  			 * Do not list the source file as dependency, so that
  			 * kbuild is not confused if a .c file is rewritten
  			 * into .S or vice versa. Storing it in source_* is
  			 * needed for modpost to compute srcversions.
  			 */
  			if (is_first_dep) {

  				/*

  				 * If processing the concatenation of multiple
  				 * dependency files, only process the first
  				 * target name, which will be the original
  				 * source name, and ignore any other target
  				 * names, which will be intermediate temporary
  				 * files.

  				 */

  				if (!saw_any_target) {
  					saw_any_target = 1;

  					xprintf("source_%s := %s
  
  ",
  						target, m);
  					xprintf("deps_%s := \\
  ", target);

  				}
  				is_first_dep = 0;
  			} else {

  				xprintf("  %s \\
  ", m);

  			}

  
  			buf = read_file(m);
  			parse_config_file(buf);
  			free(buf);

  		}

  
  		if (is_last)
  			break;

  		/*
  		 * Start searching for next token immediately after the first
  		 * "whitespace" character that follows this token.
  		 */

  		m = p + 1;
  	}

  
  	if (!saw_any_target) {
  		fprintf(stderr, "fixdep: parse error; no targets found
  ");
  		exit(1);
  	}

  	xprintf("
  %s: $(deps_%s)
  
  ", target, target);
  	xprintf("$(deps_%s):
  ", target);

  }

  int main(int argc, char *argv[])
  {

  	const char *depfile, *target, *cmdline;

  	void *buf;

  	if (argc != 4)

  		usage();
  
  	depfile = argv[1];
  	target = argv[2];
  	cmdline = argv[3];

  	xprintf("cmd_%s := %s
  
  ", target, cmdline);

  
  	buf = read_file(depfile);

  	parse_dep_file(buf, target);

  	free(buf);

  
  	return 0;
  }