hcache.c

C++的一个好库。。。现在很流行

/*
 * This file has been donated to Jam.
 */

# include "jam.h"
# include "lists.h"
# include "parse.h"
# include "rules.h"
# include "regexp.h"
# include "headers.h"
# include "newstr.h"
# include "hash.h"
# include "hcache.h"
# include "variable.h"
# include "search.h"

#ifdef OPT_HEADER_CACHE_EXT

/*
 * Craig W. McPheeters, Alias|Wavefront.
 *
 * hcache.c hcache.h - handle cacheing of #includes in source files
 *
 * Create a cache of files scanned for headers.  When starting jam,
 * look for the cache file and load it if present.  When finished the
 * binding phase, create a new header cache.  The cache contains
 * files, their timestamps and the header files found in their scan.
 * During the binding phase of jam, look in the header cache first for
 * the headers contained in a file.  If the cache is present and
 * valid, use its contents.  This results in dramatic speedups with
 * large projects (eg. 3min -> 1min startup for one project.)
 *
 * External routines:
 *    hcache_init() - read and parse the local .jamdeps file.
 *    hcache_done() - write a new .jamdeps file
 *    hcache() - return list of headers on target.  Use cache or do a scan.
 *    
 * The dependency file format is an ascii file with 1 line per target.
 * Each line has the following fields:
 * @boundname@ timestamp @file@ @file@ @file@ ... \n
 * */

struct hcachedata {
    char		*boundname;
    time_t		time;
    LIST		*includes;
    LIST		*hdrscan; /* the HDRSCAN value for this target */
    int			age;	/* if too old, we'll remove it from cache */
    struct hcachedata	*next;
} ;

typedef struct hcachedata HCACHEDATA ;


static struct hash *hcachehash = 0;
static HCACHEDATA  *hcachelist = 0; 

static int queries = 0;
static int hits = 0;

#define CACHE_FILE_VERSION "version 4"
#define CACHE_RECORD_HEADER "header"
#define CACHE_RECORD_END "end"

/*
 * Return the name of the header cache file.  May return NULL.
 *
 * The user sets this by setting the HCACHEFILE variable in a Jamfile.
 * We cache the result so the user can't change the cache file during
 * header scanning.
 */
static char*
cache_name(void)
{
    static char* name = 0;
    if (!name) {
	LIST *hcachevar = var_get("HCACHEFILE");

	if (hcachevar) {
	    TARGET *t = bindtarget( hcachevar->string );

	    pushsettings( t->settings );
        /* Don't expect cache file to be generated, so pass 0
           as third argument to search. */
	    t->boundname = search( t->name, &t->time, 0 );
	    popsettings( t->settings );

	    if (hcachevar) {
		name = copystr(t->boundname);
	    }
	}
    }
    return name;
}

/*
 * Return the maximum age a cache entry can have before it is purged
 * from the cache.
 */
static int
cache_maxage(void)
{
    int age = 100;
    LIST *var = var_get("HCACHEMAXAGE");

    if (var) {
	age = atoi(var->string);
	if (age < 0)
	    age = 0;
    }

    return age;
}

/*
 * Read a netstring.  The caveat is that the string can't contain
 * ASCII 0.  The returned value is as returned by newstr(), so it need
 * not be freed.
 */
char*
read_netstring(FILE* f)
{
    unsigned long len;
    static char* buf = NULL;
    static unsigned long buf_len = 0;

    if (fscanf(f, " %9lu", &len) != 1)
	return NULL;
    if (fgetc(f) != (int)'\t')
	return NULL;

    if (len > 1024 * 64)
	return NULL;		/* sanity check */

    if (len > buf_len)
    {
	unsigned long new_len = buf_len * 2;
	if (new_len < len)
	    new_len = len;
	buf = (char*)realloc(buf, new_len + 1);
	if (buf)
	    buf_len = new_len;
    }

    if (!buf)
	return NULL;

    if (fread(buf, 1, len, f) != len)
	return NULL;
    if (fgetc(f) != (int)'\n')
	return NULL;

    buf[len] = 0;
    return newstr(buf);
}

/*
 * Write a netstring.
 */
void
write_netstring(FILE* f, const char* s)
{
    if (!s)
	s = "";
    fprintf(f, "%lu\t%s\n", strlen(s), s);
}

void
hcache_init()
{
    HCACHEDATA  cachedata, *c;
    FILE	*f;
    char	*version;
    int		header_count = 0;
    char*	hcachename;

    hcachehash = hashinit (sizeof (HCACHEDATA), "hcache");

    if (! (hcachename = cache_name()))
	return;

    if (! (f = fopen (hcachename, "rb" )))
	return;
    
    version = read_netstring(f);
    if (!version || strcmp(version, CACHE_FILE_VERSION)) {
	fclose(f);
	return;
    }

    while (1)
    {
	char* record_type;
	char *time_str;
	char *age_str;
	char *includes_count_str;
	char *hdrscan_count_str;
	int i, count;
	LIST *l;

	record_type = read_netstring(f);
	if (!record_type) {
	    fprintf(stderr, "invalid %s\n", hcachename);
	    goto bail;
	}
	if (!strcmp(record_type, CACHE_RECORD_END)) {
	    break;
	}
	if (strcmp(record_type, CACHE_RECORD_HEADER)) {
	    fprintf(stderr, "invalid %s with record separator <%s>\n",
		    hcachename, record_type ? record_type : "<null>");
	    goto bail;
	}
	
	c = &cachedata;
	    
	c->boundname = read_netstring(f);
	time_str = read_netstring(f);
	age_str = read_netstring(f);
	includes_count_str = read_netstring(f);
	
	if (!c->boundname || !time_str || !age_str
	    || !includes_count_str)
	{
	    fprintf(stderr, "invalid %s\n", hcachename);
	    goto bail;
	}

	c->time = atoi(time_str);
	c->age = atoi(age_str) + 1;

	count = atoi(includes_count_str);
	for (l = 0, i = 0; i < count; i++) {
	    char* s = read_netstring(f);
	    if (!s) {
		fprintf(stderr, "invalid %s\n", hcachename);
		goto bail;
	    }
	    l = list_new(l, s);
	}
	c->includes = l;

	hdrscan_count_str = read_netstring(f);
	if (!includes_count_str) {
	    list_free(c->includes);
	    fprintf(stderr, "invalid %s\n", hcachename);
	    goto bail;
	}

	count = atoi(hdrscan_count_str);
	for (l = 0, i = 0; i < count; i++) {
	    char* s = read_netstring(f);
	    if (!s) {
		fprintf(stderr, "invalid %s\n", hcachename);
		goto bail;
	    }
	    l = list_new(l, s);
	}
	c->hdrscan = l;

	if (!hashenter(hcachehash, (HASHDATA **)&c)) {
	    fprintf(stderr, "can't insert header cache item, bailing on %s\n",
		    hcachename);
	    goto bail;
	}

	c->next = hcachelist;
	hcachelist = c;

	header_count++;
    }

    if (DEBUG_HEADER) {
	printf("hcache read from file %s\n", hcachename);
    }
    
 bail:
    fclose(f);
}

void
hcache_done()
{
    FILE	*f;
    HCACHEDATA  *c;
    int 	header_count = 0;
    char*	hcachename;
    int		maxage;
    
    if (!hcachehash)
	return;

    if (! (hcachename = cache_name()))
	return;

    if (! (f = fopen (hcachename, "wb" )))
	return;

    maxage = cache_maxage();

    /* print out the version */
    write_netstring(f, CACHE_FILE_VERSION);

    c = hcachelist;
    for (c = hcachelist; c; c = c->next) {
	LIST	*l;
	char time_str[30];
	char age_str[30];
	char includes_count_str[30];
	char hdrscan_count_str[30];

	if (maxage == 0)
	    c->age = 0;
	else if (c->age > maxage)
	    continue;

	sprintf(includes_count_str, "%lu", list_length(c->includes));
	sprintf(hdrscan_count_str, "%lu", list_length(c->hdrscan));
	sprintf(time_str, "%lu", c->time);
	sprintf(age_str, "%lu", c->age);

	write_netstring(f, CACHE_RECORD_HEADER);
	write_netstring(f, c->boundname);
	write_netstring(f, time_str);
	write_netstring(f, age_str);
	write_netstring(f, includes_count_str);
	for (l = c->includes; l; l = list_next(l)) {
	    write_netstring(f, l->string);
	}
	write_netstring(f, hdrscan_count_str);
	for (l = c->hdrscan; l; l = list_next(l)) {
	    write_netstring(f, l->string);
	}
	fputs("\n", f);
	header_count++;
    }
    write_netstring(f, CACHE_RECORD_END);

    if (DEBUG_HEADER) {
	printf("hcache written to %s.   %d dependencies, %.0f%% hit rate\n",
	       hcachename, header_count,
	       queries ? 100.0 * hits / queries : 0);
    }

    fclose (f);
}

LIST *
hcache (TARGET *t, int rec, regexp *re[], LIST *hdrscan)
{
    HCACHEDATA  cachedata, *c = &cachedata;
    LIST 	*l = 0;

    ++queries;

    c->boundname = t->boundname;

    if (hashcheck (hcachehash, (HASHDATA **) &c))
    {
	if (c->time == t->time)
	{
	    LIST *l1 = hdrscan, *l2 = c->hdrscan;
	    while (l1 && l2) {
		if (l1->string != l2->string) {
		    l1 = NULL;
		} else {
		    l1 = list_next(l1);
		    l2 = list_next(l2);
		}
	    }
	    if (l1 || l2) {
		if (DEBUG_HEADER)
		    printf("HDRSCAN out of date in cache for %s\n",
			   t->boundname);

		printf("HDRSCAN out of date for %s\n", t->boundname);
		printf(" real  : ");
		list_print(hdrscan);
		printf("\n cached: ");
		list_print(c->hdrscan);
		printf("\n");

		list_free(c->includes);
		list_free(c->hdrscan);
		c->includes = 0;
		c->hdrscan = 0;
	    } else {
		if (DEBUG_HEADER)
		    printf ("using header cache for %s\n", t->boundname);
		c->age = 0;
		++hits;
		l = list_copy (0, c->includes);
		return l;
	    }
	} else {
	    if (DEBUG_HEADER)
	        printf ("header cache out of date for %s\n", t->boundname);
	    list_free (c->includes);
	    list_free(c->hdrscan);
	    c->includes = 0;
	    c->hdrscan = 0;
	}
    } else {
	if (hashenter (hcachehash, (HASHDATA **)&c)) {
	    c->boundname = newstr (c->boundname);
	    c->next = hcachelist;
	    hcachelist = c;
	}
    }

    /* 'c' points at the cache entry.  Its out of date. */

    l = headers1 (0, t->boundname, rec, re);

    c->time = t->time;
    c->age = 0;
    c->includes = list_copy (0, l);
    c->hdrscan = list_copy(0, hdrscan);

    return l;
}

#endif