Add virStringSearch method for regex matching

Add a virStringSearch method to virstring.{c,h} which performs
a regex match against a string and returns the matching substrings.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

po/POTFILES.in

@@ -192,6 +192,7 @@ src/util/virscsi.c
 src/util/virsocketaddr.c
 src/util/virstatslinux.c
 src/util/virstoragefile.c
+src/util/virstring.c
 src/util/virsysinfo.c
 src/util/virerror.c
 src/util/virerror.h

src/libvirt_private.syms

@@ -1798,6 +1798,7 @@ virStringArrayHasString;
 virStringFreeList;
 virStringJoin;
 virStringListLength;
+virStringSearch;
 virStringSortCompare;
 virStringSortRevCompare;
 virStringSplit;

src/util/virstring.c

@@ -23,12 +23,14 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <regex.h>
 
 #include "c-ctype.h"
 #include "virstring.h"
 #include "viralloc.h"
 #include "virbuffer.h"
 #include "virerror.h"
+#include "virlog.h"
 
 #define VIR_FROM_THIS VIR_FROM_NONE
 
@@ -645,3 +647,105 @@ int virStringSortRevCompare(const void *a, const void *b)
 
     return strcmp(*sb, *sa);
 }
+
+/**
+ * virStringSearch:
+ * @str: string to search
+ * @regexp: POSIX Extended regular expression pattern used for matching
+ * @max_matches: maximum number of substrings to return
+ * @result: pointer to an array to be filled with NULL terminated list of matches
+ *
+ * Performs a POSIX extended regex search against a string and return all matching substrings.
+ * The @result value should be freed with virStringFreeList() when no longer
+ * required.
+ *
+ * @code
+ *  char *source = "6853a496-1c10-472e-867a-8244937bd6f0
+ *                  773ab075-4cd7-4fc2-8b6e-21c84e9cb391
+ *                  bbb3c75c-d60f-43b0-b802-fd56b84a4222
+ *                  60c04aa1-0375-4654-8d9f-e149d9885273
+ *                  4548d465-9891-4c34-a184-3b1c34a26aa8";
+ *  char **matches = NULL;
+ *  virStringSearch(source,
+ *                  "([a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12})",
+ *                  3,
+ *                  &matches);
+ *
+ *  // matches[0] == "6853a496-1c10-472e-867a-8244937bd6f0";
+ *  // matches[1] == "773ab075-4cd7-4fc2-8b6e-21c84e9cb391";
+ *  // matches[2] == "bbb3c75c-d60f-43b0-b802-fd56b84a4222"
+ *  // matches[3] == NULL;
+ *
+ *  virStringFreeList(matches);
+ * @endcode
+ *
+ * Returns: -1 on error, or number of matches
+ */
+ssize_t
+virStringSearch(const char *str,
+                const char *regexp,
+                size_t max_matches,
+                char ***matches)
+{
+    regex_t re;
+    regmatch_t rem;
+    size_t nmatches = 0;
+    ssize_t ret = -1;
+    int rv = -1;
+
+    *matches = NULL;
+
+    VIR_DEBUG("search '%s' for '%s'", str, regexp);
+
+    if ((rv = regcomp(&re, regexp, REG_EXTENDED)) != 0) {
+        char error[100];
+        regerror(rv, &re, error, sizeof(error));
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Error while compiling regular expression '%s': %s"),
+                       regexp, error);
+        return -1;
+    }
+
+    if (re.re_nsub != 1) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Regular expression '%s' must have exactly 1 match group, not %zu"),
+                       regexp, re.re_nsub);
+        goto cleanup;
+    }
+
+    /* '*matches' must always be NULL terminated in every iteration
+     * of the loop, so start by allocating 1 element
+     */
+    if (VIR_EXPAND_N(*matches, nmatches, 1) < 0)
+        goto cleanup;
+
+    while ((nmatches - 1) < max_matches) {
+        char *match;
+
+        if (regexec(&re, str, 1, &rem, 0) != 0)
+            break;
+
+        if (VIR_EXPAND_N(*matches, nmatches, 1) < 0)
+            goto cleanup;
+
+        if (VIR_STRNDUP(match, str + rem.rm_so,
+                        rem.rm_eo - rem.rm_so) < 0)
+            goto cleanup;
+
+        VIR_DEBUG("Got '%s'", match);
+
+        (*matches)[nmatches-2] = match;
+
+        str = str + rem.rm_eo;
+    }
+
+    ret = nmatches - 1; /* don't count the trailing null */
+
+cleanup:
+    regfree(&re);
+    if (ret < 0) {
+        virStringFreeList(*matches);
+        *matches = NULL;
+    }
+    return ret;
+}

src/util/virstring.h

@@ -226,4 +226,11 @@ size_t virStringListLength(char **strings);
 int virStringSortCompare(const void *a, const void *b);
 int virStringSortRevCompare(const void *a, const void *b);
 
+ssize_t virStringSearch(const char *str,
+                        const char *regexp,
+                        size_t max_results,
+                        char ***matches)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(4);
+
+
 #endif /* __VIR_STRING_H__ */

tests/virstringtest.c

@@ -274,6 +274,70 @@ testStringSortCompare(const void *opaque ATTRIBUTE_UNUSED)
 }
 
 
+struct stringSearchData {
+    const char *str;
+    const char *regexp;
+    size_t maxMatches;
+    size_t expectNMatches;
+    const char **expectMatches;
+    bool expectError;
+};
+
+static int
+testStringSearch(const void *opaque ATTRIBUTE_UNUSED)
+{
+    const struct stringSearchData *data = opaque;
+    char **matches = NULL;
+    ssize_t nmatches;
+    int ret = -1;
+
+    nmatches = virStringSearch(data->str, data->regexp,
+                               data->maxMatches, &matches);
+
+    if (data->expectError) {
+        if (nmatches != -1) {
+            fprintf(stderr, "expected error on %s but got %zd matches\n",
+                    data->str, nmatches);
+            goto cleanup;
+        }
+    } else {
+        size_t i;
+
+        if (nmatches < 0) {
+            fprintf(stderr, "expected %zu matches on %s but got error\n",
+                    data->expectNMatches, data->str);
+            goto cleanup;
+        }
+
+        if (nmatches != data->expectNMatches) {
+            fprintf(stderr, "expected %zu matches on %s but got %zd\n",
+                    data->expectNMatches, data->str, nmatches);
+            goto cleanup;
+        }
+
+        if (virStringListLength(matches) != nmatches) {
+            fprintf(stderr, "expected %zu matches on %s but got %zd matches\n",
+                    data->expectNMatches, data->str,
+                    virStringListLength(matches));
+            goto cleanup;
+        }
+
+        for (i = 0; i < nmatches; i++) {
+            if (STRNEQ(matches[i], data->expectMatches[i])) {
+                fprintf(stderr, "match %zu expected '%s' but got '%s'\n",
+                        i, data->expectMatches[i], matches[i]);
+                goto cleanup;
+            }
+        }
+    }
+
+    ret = 0;
+
+ cleanup:
+    virStringFreeList(matches);
+    return ret;
+}
+
 static int
 mymain(void)
 {
@@ -328,6 +392,42 @@ mymain(void)
     if (virtTestRun("virStringSortCompare", testStringSortCompare, NULL) < 0)
         ret = -1;
 
+
+#define TEST_SEARCH(s, r, x, n, m, e)                                   \
+    do {                                                                \
+        struct stringSearchData data = {                                \
+            .str = s,                                                   \
+            .maxMatches = x,                                            \
+            .regexp = r,                                                \
+            .expectNMatches = n,                                        \
+            .expectMatches = m,                                         \
+            .expectError = e,                                           \
+        };                                                              \
+        if (virtTestRun("virStringSearch " s, testStringSearch, &data) < 0) \
+            ret = -1;                                                   \
+    } while (0)
+
+    /* error due to missing () in regexp */
+    TEST_SEARCH("foo", "bar", 10, 0, NULL, true);
+
+    /* error due to too many () in regexp */
+    TEST_SEARCH("foo", "(b)(a)(r)", 10, 0, NULL, true);
+
+    /* None matching */
+    TEST_SEARCH("foo", "(bar)", 10, 0, NULL, false);
+
+    /* Full match */
+    const char *matches1[] = { "foo" };
+    TEST_SEARCH("foo", "(foo)", 10, 1, matches1, false);
+
+    /* Multi matches */
+    const char *matches2[] = { "foo", "bar", "eek" };
+    TEST_SEARCH("1foo2bar3eek", "([a-z]+)", 10, 3, matches2, false);
+
+    /* Multi matches, limited returns */
+    const char *matches3[] = { "foo", "bar" };
+    TEST_SEARCH("1foo2bar3eek", "([a-z]+)", 2, 2, matches3, false);
+
     return ret==0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }