Add hash table support as base for new environment code

This implementation is based on code from uClibc-0.9.30.3 but was
modified and extended for use within U-Boot.

Major modifications and extensions:

* hsearch() [modified / extended]:
  - While the standard version does not make any assumptions about
    the type of the stored data objects at all, this implementation
    works with NUL terminated strings only.
  - Instead of storing just pointers to the original objects, we
    create local copies so the caller does not need to care about the
    data any more.
  - The standard implementation does not provide a way to update an
    existing entry.  This version will create a new entry or update an
    existing one when both "action == ENTER" and "item.data != NULL".
  - hsearch_r(): Instead of returning 1 on success, we return the
    index into the internal hash table, which is also guaranteed to be
    positive.  This allows us direct access to the found hash table
    slot for example for functions like hdelete().
* hdelete() [added]:
  - The standard implementation of hsearch(3) does not provide any way
    to delete any entries from the hash table.  We extend the code to
    do that.
* hexport() [added]:
  - Export the data stored in the hash table in linearized form:
    Entries are exported as "name=value" strings, separated by an
    arbitrary (non-NUL, of course) separator character. This allows to
    use this function both when formatting the U-Boot environment for
    external storage (using '\0' as separator), but also when using it
    for the "printenv" command to print all variables, simply by using
    as '\n" as separator. This can also be used for new features like
    exporting the environment data as text file, including the option
    for later re-import.
  - The entries in the result list will be sorted by ascending key
    values.
* himport() [added]:
  - Import linearized data into hash table.  This is the inverse
    function to hexport(): it takes a linear list of "name=value"
    pairs and creates hash table entries from it.
  - Entries without "value", i. e. consisting of only "name" or
    "name=", will cause this entry to be deleted from the hash table.
  - The "flag" argument can be used to control the behaviour: when
    the H_NOCLEAR bit is set, then an existing hash table will kept,
    i. e. new data will be added to an existing hash table;
    otherwise, old data will be discarded and a new hash table will
    be created.
  - The separator character for the "name=value" pairs can be
    selected, so we both support importing from externally stored
    environment data (separated by NUL characters) and from plain text
    files (entries separated by newline characters).
  - To allow for nicely formatted text input, leading white space
    (sequences of SPACE and TAB chars) is ignored, and entries
    starting (after removal of any leading white space) with a '#'
    character are considered comments and ignored.
  - NOTE: this means that a variable name cannot start with a '#'
    character.
  - When using a non-NUL separator character, backslash is used as
    escape character in the value part, allowing for example fo
    multi-line values.
  - In theory, arbitrary separator characters can be used, but only
    '\0' and '\n' have really been tested.

Signed-off-by: Wolfgang Denk <wd@denx.de>

2 files changed, 722 insertions, 0 deletions

diff --git a/lib/Makefile b/lib/Makefile
index 2d969a3d77d..a8de3e1df6d 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -39,6 +39,7 @@ COBJS-y += display_options.o
 COBJS-y += div64.o
 COBJS-y += errno.o
 COBJS-$(CONFIG_GZIP) += gunzip.o
+COBJS-y += hashtable.o
 COBJS-$(CONFIG_LMB) += lmb.o
 COBJS-y += ldiv.o
 COBJS-$(CONFIG_MD5) += md5.o
diff --git a/lib/hashtable.c b/lib/hashtable.c
new file mode 100644
index 00000000000..2f3b5c8d102
--- /dev/null
+++ b/lib/hashtable.c
@@ -0,0 +1,721 @@
+/*
+ * This implementation is based on code from uClibc-0.9.30.3 but was
+ * modified and extended for use within U-Boot.
+ *
+ * Copyright (C) 2010 Wolfgang Denk <wd@denx.de>
+ *
+ * Original license header:
+ *
+ * Copyright (C) 1993, 1995, 1996, 1997, 2002 Free Software Foundation, Inc.
+ * This file is part of the GNU C Library.
+ * Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1993.
+ *
+ * The GNU C Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * The GNU C Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with the GNU C Library; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ * 02111-1307 USA.
+ */
+
+#include <errno.h>
+#include <malloc.h>
+
+#ifdef USE_HOSTCC		/* HOST build */
+# include <string.h>
+# include <assert.h>
+
+# ifndef debug
+#  ifdef DEBUG
+#   define debug(fmt,args...)	printf(fmt ,##args)
+#  else
+#   define debug(fmt,args...)
+#  endif
+# endif
+#else				/* U-Boot build */
+# include <common.h>
+# include <linux/string.h>
+#endif
+
+#include "search.h"
+
+/*
+ * [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
+ * [Knuth]            The Art of Computer Programming, part 3 (6.4)
+ */
+
+/*
+ * The non-reentrant version use a global space for storing the hash table.
+ */
+static struct hsearch_data htab;
+
+/*
+ * The reentrant version has no static variables to maintain the state.
+ * Instead the interface of all functions is extended to take an argument
+ * which describes the current status.
+ */
+typedef struct _ENTRY {
+	unsigned int used;
+	ENTRY entry;
+} _ENTRY;
+
+
+/*
+ * hcreate()
+ */
+
+/*
+ * For the used double hash method the table size has to be a prime. To
+ * correct the user given table size we need a prime test.  This trivial
+ * algorithm is adequate because
+ * a)  the code is (most probably) called a few times per program run and
+ * b)  the number is small because the table must fit in the core
+ * */
+static int isprime(unsigned int number)
+{
+	/* no even number will be passed */
+	unsigned int div = 3;
+
+	while (div * div < number && number % div != 0)
+		div += 2;
+
+	return number % div != 0;
+}
+
+int hcreate(size_t nel)
+{
+	return hcreate_r(nel, &htab);
+}
+
+/*
+ * Before using the hash table we must allocate memory for it.
+ * Test for an existing table are done. We allocate one element
+ * more as the found prime number says. This is done for more effective
+ * indexing as explained in the comment for the hsearch function.
+ * The contents of the table is zeroed, especially the field used
+ * becomes zero.
+ */
+int hcreate_r(size_t nel, struct hsearch_data *htab)
+{
+	/* Test for correct arguments.  */
+	if (htab == NULL) {
+		__set_errno(EINVAL);
+		return 0;
+	}
+
+	/* There is still another table active. Return with error. */
+	if (htab->table != NULL)
+		return 0;
+
+	/* Change nel to the first prime number not smaller as nel. */
+	nel |= 1;		/* make odd */
+	while (!isprime(nel))
+		nel += 2;
+
+	htab->size = nel;
+	htab->filled = 0;
+
+	/* allocate memory and zero out */
+	htab->table = (_ENTRY *) calloc(htab->size + 1, sizeof(_ENTRY));
+	if (htab->table == NULL)
+		return 0;
+
+	/* everything went alright */
+	return 1;
+}
+
+
+/*
+ * hdestroy()
+ */
+void hdestroy(void)
+{
+	hdestroy_r(&htab);
+}
+
+/*
+ * After using the hash table it has to be destroyed. The used memory can
+ * be freed and the local static variable can be marked as not used.
+ */
+void hdestroy_r(struct hsearch_data *htab)
+{
+	int i;
+
+	/* Test for correct arguments.  */
+	if (htab == NULL) {
+		__set_errno(EINVAL);
+		return;
+	}
+
+	/* free used memory */
+	for (i = 1; i <= htab->size; ++i) {
+		if (htab->table[i].used) {
+			ENTRY *ep = &htab->table[i].entry;
+
+			free(ep->key);
+			free(ep->data);
+		}
+	}
+	free(htab->table);
+
+	/* the sign for an existing table is an value != NULL in htable */
+	htab->table = NULL;
+}
+
+/*
+ * hsearch()
+ */
+
+/*
+ * This is the search function. It uses double hashing with open addressing.
+ * The argument item.key has to be a pointer to an zero terminated, most
+ * probably strings of chars. The function for generating a number of the
+ * strings is simple but fast. It can be replaced by a more complex function
+ * like ajw (see [Aho,Sethi,Ullman]) if the needs are shown.
+ *
+ * We use an trick to speed up the lookup. The table is created by hcreate
+ * with one more element available. This enables us to use the index zero
+ * special. This index will never be used because we store the first hash
+ * index in the field used where zero means not used. Every other value
+ * means used. The used field can be used as a first fast comparison for
+ * equality of the stored and the parameter value. This helps to prevent
+ * unnecessary expensive calls of strcmp.
+ *
+ * This implementation differs from the standard library version of
+ * this function in a number of ways:
+ *
+ * - While the standard version does not make any assumptions about
+ *   the type of the stored data objects at all, this implementation
+ *   works with NUL terminated strings only.
+ * - Instead of storing just pointers to the original objects, we
+ *   create local copies so the caller does not need to care about the
+ *   data any more.
+ * - The standard implementation does not provide a way to update an
+ *   existing entry.  This version will create a new entry or update an
+ *   existing one when both "action == ENTER" and "item.data != NULL".
+ * - Instead of returning 1 on success, we return the index into the
+ *   internal hash table, which is also guaranteed to be positive.
+ *   This allows us direct access to the found hash table slot for
+ *   example for functions like hdelete().
+ */
+
+ENTRY *hsearch(ENTRY item, ACTION action)
+{
+	ENTRY *result;
+
+	(void) hsearch_r(item, action, &result, &htab);
+
+	return result;
+}
+
+int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
+	      struct hsearch_data *htab)
+{
+	unsigned int hval;
+	unsigned int count;
+	unsigned int len = strlen(item.key);
+	unsigned int idx;
+
+	/* Compute an value for the given string. Perhaps use a better method. */
+	hval = len;
+	count = len;
+	while (count-- > 0) {
+		hval <<= 4;
+		hval += item.key[count];
+	}
+
+	/*
+	 * First hash function:
+	 * simply take the modul but prevent zero.
+	 */
+	hval %= htab->size;
+	if (hval == 0)
+		++hval;
+
+	/* The first index tried. */
+	idx = hval;
+
+	if (htab->table[idx].used) {
+		/*
+                 * Further action might be required according to the
+		 * action value.
+		 */
+		unsigned hval2;
+
+		if (htab->table[idx].used == hval
+		    && strcmp(item.key, htab->table[idx].entry.key) == 0) {
+			/* Overwrite existing value? */
+			if ((action == ENTER) && (item.data != NULL)) {
+				free(htab->table[idx].entry.data);
+				htab->table[idx].entry.data =
+					strdup(item.data);
+				if (!htab->table[idx].entry.data) {
+					__set_errno(ENOMEM);
+					*retval = NULL;
+					return 0;
+				}
+			}
+			/* return found entry */
+			*retval = &htab->table[idx].entry;
+			return idx;
+		}
+
+		/*
+		 * Second hash function:
+		 * as suggested in [Knuth]
+		 */
+		hval2 = 1 + hval % (htab->size - 2);
+
+		do {
+			/*
+                         * Because SIZE is prime this guarantees to
+                         * step through all available indices.
+			 */
+			if (idx <= hval2)
+				idx = htab->size + idx - hval2;
+			else
+				idx -= hval2;
+
+			/*
+			 * If we visited all entries leave the loop
+			 * unsuccessfully.
+			 */
+			if (idx == hval)
+				break;
+
+			/* If entry is found use it. */
+			if ((htab->table[idx].used == hval)
+			    && strcmp(item.key, htab->table[idx].entry.key) == 0) {
+				/* Overwrite existing value? */
+				if ((action == ENTER) && (item.data != NULL)) {
+					free(htab->table[idx].entry.data);
+					htab->table[idx].entry.data =
+						strdup(item.data);
+					if (!htab->table[idx].entry.data) {
+						__set_errno(ENOMEM);
+						*retval = NULL;
+						return 0;
+					}
+				}
+				/* return found entry */
+				*retval = &htab->table[idx].entry;
+				return idx;
+			}
+		}
+		while (htab->table[idx].used);
+	}
+
+	/* An empty bucket has been found. */
+	if (action == ENTER) {
+		/*
+                 * If table is full and another entry should be
+                 * entered return with error.
+		 */
+		if (htab->filled == htab->size) {
+			__set_errno(ENOMEM);
+			*retval = NULL;
+			return 0;
+		}
+
+		/*
+		 * Create new entry;
+		 * create copies of item.key and item.data
+		 */
+		htab->table[idx].used = hval;
+		htab->table[idx].entry.key = strdup(item.key);
+		htab->table[idx].entry.data = strdup(item.data);
+		if (!htab->table[idx].entry.key ||
+		    !htab->table[idx].entry.data) {
+			__set_errno(ENOMEM);
+			*retval = NULL;
+			return 0;
+		}
+
+		++htab->filled;
+
+		/* return new entry */
+		*retval = &htab->table[idx].entry;
+		return 1;
+	}
+
+	__set_errno(ESRCH);
+	*retval = NULL;
+	return 0;
+}
+
+
+/*
+ * hdelete()
+ */
+
+/*
+ * The standard implementation of hsearch(3) does not provide any way
+ * to delete any entries from the hash table.  We extend the code to
+ * do that.
+ */
+
+int hdelete(const char *key)
+{
+	return hdelete_r(key, &htab);
+}
+
+int hdelete_r(const char *key, struct hsearch_data *htab)
+{
+	ENTRY e, *ep;
+	int idx;
+
+	debug("hdelete: DELETE key \"%s\"\n", key);
+
+	e.key = (char *)key;
+
+	if ((idx = hsearch_r(e, FIND, &ep, htab)) == 0) {
+		__set_errno(ESRCH);
+		return 0;	/* not found */
+	}
+
+	/* free used ENTRY */
+	debug("hdelete: DELETING key \"%s\"\n", key);
+
+	free(ep->key);
+	free(ep->data);
+	htab->table[idx].used = 0;
+
+	--htab->filled;
+
+	return 1;
+}
+
+/*
+ * hexport()
+ */
+
+/*
+ * Export the data stored in the hash table in linearized form.
+ *
+ * Entries are exported as "name=value" strings, separated by an
+ * arbitrary (non-NUL, of course) separator character. This allows to
+ * use this function both when formatting the U-Boot environment for
+ * external storage (using '\0' as separator), but also when using it
+ * for the "printenv" command to print all variables, simply by using
+ * as '\n" as separator. This can also be used for new features like
+ * exporting the environment data as text file, including the option
+ * for later re-import.
+ *
+ * The entries in the result list will be sorted by ascending key
+ * values.
+ *
+ * If the separator character is different from NUL, then any
+ * separator characters and backslash characters in the values will
+ * be escaped by a preceeding backslash in output. This is needed for
+ * example to enable multi-line values, especially when the output
+ * shall later be parsed (for example, for re-import).
+ *
+ * There are several options how the result buffer is handled:
+ *
+ * *resp  size
+ * -----------
+ *  NULL    0	A string of sufficient length will be allocated.
+ *  NULL   >0	A string of the size given will be
+ *		allocated. An error will be returned if the size is
+ *		not sufficient.  Any unused bytes in the string will
+ *		be '\0'-padded.
+ * !NULL    0	The user-supplied buffer will be used. No length
+ *		checking will be performed, i. e. it is assumed that
+ *		the buffer size will always be big enough. DANGEROUS.
+ * !NULL   >0	The user-supplied buffer will be used. An error will
+ *		be returned if the size is not sufficient.  Any unused
+ *		bytes in the string will be '\0'-padded.
+ */
+
+ssize_t hexport(const char sep, char **resp, size_t size)
+{
+	return hexport_r(&htab, sep, resp, size);
+}
+
+static int cmpkey(const void *p1, const void *p2)
+{
+	ENTRY *e1 = *(ENTRY **) p1;
+	ENTRY *e2 = *(ENTRY **) p2;
+
+	return (strcmp(e1->key, e2->key));
+}
+
+ssize_t hexport_r(struct hsearch_data *htab, const char sep,
+		 char **resp, size_t size)
+{
+	ENTRY *list[htab->size];
+	char *res, *p;
+	size_t totlen;
+	int i, n;
+
+	/* Test for correct arguments.  */
+	if ((resp == NULL) || (htab == NULL)) {
+		__set_errno(EINVAL);
+		return (-1);
+	}
+
+	debug("EXPORT  table = %p, htab.size = %d, htab.filled = %d, size = %d\n",
+		htab, htab->size, htab->filled, size);
+	/*
+	 * Pass 1:
+	 * search used entries,
+	 * save addresses and compute total length
+	 */
+	for (i = 1, n = 0, totlen = 0; i <= htab->size; ++i) {
+
+		if (htab->table[i].used) {
+			ENTRY *ep = &htab->table[i].entry;
+
+			list[n++] = ep;
+
+			totlen += strlen(ep->key) + 2;
+
+			if (sep == '\0') {
+				totlen += strlen(ep->data);
+			} else {	/* check if escapes are needed */
+				char *s = ep->data;
+
+				while (*s) {
+					++totlen;
+					/* add room for needed escape chars */
+					if ((*s == sep) || (*s == '\\'))
+						++totlen;
+					++s;
+				}
+			}
+			totlen += 2;	/* for '=' and 'sep' char */
+		}
+	}
+
+#ifdef DEBUG
+	/* Pass 1a: print unsorted list */
+	printf("Unsorted: n=%d\n", n);
+	for (i = 0; i < n; ++i) {
+		printf("\t%3d: %p ==> %-10s => %s\n",
+		       i, list[i], list[i]->key, list[i]->data);
+	}
+#endif
+
+	/* Sort list by keys */
+	qsort(list, n, sizeof(ENTRY *), cmpkey);
+
+	/* Check if the user supplied buffer size is sufficient */
+	if (size) {
+		if (size < totlen + 1) {	/* provided buffer too small */
+			debug("### buffer too small: %d, but need %d\n",
+				size, totlen + 1);
+			__set_errno(ENOMEM);
+			return (-1);
+		}
+	} else {
+		size = totlen + 1;
+	}
+
+	/* Check if the user provided a buffer */
+	if (*resp) {
+		/* yes; clear it */
+		res = *resp;
+		memset(res, '\0', size);
+	} else {
+		/* no, allocate and clear one */
+		*resp = res = calloc(1, size);
+		if (res == NULL) {
+			__set_errno(ENOMEM);
+			return (-1);
+		}
+	}
+	/*
+	 * Pass 2:
+	 * export sorted list of result data
+	 */
+	for (i = 0, p = res; i < n; ++i) {
+		char *s;
+
+		s = list[i]->key;
+		while (*s)
+			*p++ = *s++;
+		*p++ = '=';
+
+		s = list[i]->data;
+
+		while (*s) {
+			if ((*s == sep) || (*s == '\\'))
+				*p++ = '\\';	/* escape */
+			*p++ = *s++;
+		}
+		*p++ = sep;
+	}
+	*p = '\0';		/* terminate result */
+
+	return size;
+}
+
+
+/*
+ * himport()
+ */
+
+/*
+ * Import linearized data into hash table.
+ *
+ * This is the inverse function to hexport(): it takes a linear list
+ * of "name=value" pairs and creates hash table entries from it.
+ *
+ * Entries without "value", i. e. consisting of only "name" or
+ * "name=", will cause this entry to be deleted from the hash table.
+ *
+ * The "flag" argument can be used to control the behaviour: when the
+ * H_NOCLEAR bit is set, then an existing hash table will kept, i. e.
+ * new data will be added to an existing hash table; otherwise, old
+ * data will be discarded and a new hash table will be created.
+ *
+ * The separator character for the "name=value" pairs can be selected,
+ * so we both support importing from externally stored environment
+ * data (separated by NUL characters) and from plain text files
+ * (entries separated by newline characters).
+ *
+ * To allow for nicely formatted text input, leading white space
+ * (sequences of SPACE and TAB chars) is ignored, and entries starting
+ * (after removal of any leading white space) with a '#' character are
+ * considered comments and ignored.
+ *
+ * [NOTE: this means that a variable name cannot start with a '#'
+ * character.]
+ *
+ * When using a non-NUL separator character, backslash is used as
+ * escape character in the value part, allowing for example for
+ * multi-line values.
+ *
+ * In theory, arbitrary separator characters can be used, but only
+ * '\0' and '\n' have really been tested.
+ */
+
+int himport(const char *env, size_t size, const char sep, int flag)
+{
+	return himport_r(&htab, env, size, sep, flag);
+}
+
+int himport_r(struct hsearch_data *htab,
+	      const char *env, size_t size, const char sep, int flag)
+{
+	char *data, *sp, *dp, *name, *value;
+
+	/* Test for correct arguments.  */
+	if (htab == NULL) {
+		__set_errno(EINVAL);
+		return 0;
+	}
+
+	/* we allocate new space to make sure we can write to the array */
+	if ((data = malloc(size)) == NULL) {
+		debug("himport_r: can't malloc %d bytes\n", size);
+		__set_errno(ENOMEM);
+		return 0;
+	}
+	memcpy(data, env, size);
+	dp = data;
+
+	if ((flag & H_NOCLEAR) == 0) {
+		/* Destroy old hash table if one exists */
+		debug("Destroy Hash Table: %p table = %p\n", htab,
+		       htab->table);
+		if (htab->table)
+			hdestroy_r(htab);
+	}
+
+	/*
+	 * Create new hash table (if needed).  The computation of the hash
+	 * table size is based on heuristics: in a sample of some 70+
+	 * existing systems we found an average size of 39+ bytes per entry
+	 * in the environment (for the whole key=value pair). Assuming a
+	 * size of 7 per entry (= safety factor of >5) should provide enough
+	 * safety margin for any existing environment definitons and still
+	 * allow for more than enough dynamic additions. Note that the
+	 * "size" argument is supposed to give the maximum enviroment size
+	 * (CONFIG_ENV_SIZE).
+	 */
+
+	if (!htab->table) {
+		int nent = size / 7;
+
+		debug("Create Hash Table: N=%d\n", nent);
+
+		if (hcreate_r(nent, htab) == 0) {
+			free(data);
+			return 0;
+		}
+	}
+
+	/* Parse environment; allow for '\0' and 'sep' as separators */
+	do {
+		ENTRY e, *rv;
+
+		/* skip leading white space */
+		while ((*dp == ' ') || (*dp == '\t'))
+			++dp;
+
+		/* skip comment lines */
+		if (*dp == '#') {
+			while (*dp && (*dp != sep))
+				++dp;
+			++dp;
+			continue;
+		}
+
+		/* parse name */
+		for (name = dp; *dp != '=' && *dp && *dp != sep; ++dp)
+			;
+
+		/* deal with "name" and "name=" entries (delete var) */
+		if (*dp == '\0' || *(dp + 1) == '\0' ||
+		    *dp == sep || *(dp + 1) == sep) {
+			if (*dp == '=')
+				*dp++ = '\0';
+			*dp++ = '\0';	/* terminate name */
+
+			debug("DELETE CANDIDATE: \"%s\"\n", name);
+
+			if (hdelete_r(name, htab) == 0)
+				debug("DELETE ERROR ##############################\n");
+
+			continue;
+		}
+		*dp++ = '\0';	/* terminate name */
+
+		/* parse value; deal with escapes */
+		for (value = sp = dp; *dp && (*dp != sep); ++dp) {
+			if ((*dp == '\\') && *(dp + 1))
+				++dp;
+			*sp++ = *dp;
+		}
+		*sp++ = '\0';	/* terminate value */
+		++dp;
+
+		/* enter into hash table */
+		e.key = name;
+		e.data = value;
+
+		hsearch_r(e, ENTER, &rv, htab);
+		if (rv == NULL) {
+			printf("himport_r: can't insert \"%s=%s\" into hash table\n", name, value);
+			return 0;
+		}
+
+		debug("INSERT: %p ==> name=\"%s\" value=\"%s\"\n", rv, name,
+		       value);
+		debug("        table = %p, size = %d, filled = %d\n", htab,
+		       htab->size, htab->filled);
+	} while ((dp < data + size) && *dp);	/* size check needed for text */
+						/* without '\0' termination */
+	free(data);
+
+	return 1;		/* everything OK */
+}