Implement dynstr_last_byte.

2 files changed, 83 insertions, 0 deletions

diff --git a/dynstr.c b/dynstr.c
index bff6460..b160b58 100644
--- a/dynstr.c
+++ b/dynstr.c
@@ -218,3 +218,16 @@ size_t dynstr_first_byte(Dynstr *dynstr, size_t offset, int byte)
     return (size_t) (p - dynstr->mem);
 }
 
+
+size_t dynstr_last_byte(Dynstr *dynstr, size_t offset, int byte)
+{
+    unsigned char *p;
+
+    if (offset >= dynstr->size)
+        return DYNSTR_NOT_FOUND;
+    p = memrchr(dynstr->mem + offset, byte, dynstr->size - offset);
+    if (p == NULL)
+        return DYNSTR_NOT_FOUND;
+    return (size_t) (p - dynstr->mem);
+}
+
diff --git a/unittests.c b/unittests.c
index 2e2aa78..24935ad 100644
--- a/unittests.c
+++ b/unittests.c
@@ -616,6 +616,71 @@ static int test_first_byte_only_finds_byte_inside_range(void)
 }
 
 
+static int test_last_byte_finds_byte(void)
+{
+    Dynstr *dynstr;
+    size_t offset;
+    
+    dynstr = dynstr_new_from_cstring("123456");
+    offset = dynstr_last_byte(dynstr, 0, '3');
+    FAIL_UNLESS_EQUAL(offset, 2);
+    dynstr_free(dynstr);
+    return true;
+}
+
+
+static int test_last_byte_only_finds_last_byte(void)
+{
+    Dynstr *dynstr;
+    size_t offset;
+    
+    dynstr = dynstr_new_from_cstring("123123");
+    offset = dynstr_last_byte(dynstr, 0, '3');
+    FAIL_UNLESS_EQUAL(offset, 5);
+    dynstr_free(dynstr);
+    return true;
+}
+
+
+static int test_last_byte_does_not_find_nonexistent_byte(void)
+{
+    Dynstr *dynstr;
+    size_t offset;
+    
+    dynstr = dynstr_new_from_cstring("123456");
+    offset = dynstr_last_byte(dynstr, 0, 'x');
+    FAIL_UNLESS_EQUAL(offset, DYNSTR_NOT_FOUND);
+    dynstr_free(dynstr);
+    return true;
+}
+
+
+static int test_last_byte_does_not_find_byte_outside_range(void)
+{
+    Dynstr *dynstr;
+    size_t offset;
+    
+    dynstr = dynstr_new_from_cstring("123456");
+    offset = dynstr_last_byte(dynstr, 4, '3');
+    FAIL_UNLESS_EQUAL(offset, DYNSTR_NOT_FOUND);
+    dynstr_free(dynstr);
+    return true;
+}
+
+
+static int test_last_byte_only_finds_byte_inside_range(void)
+{
+    Dynstr *dynstr;
+    size_t offset;
+    
+    dynstr = dynstr_new_from_cstring("123123");
+    offset = dynstr_last_byte(dynstr, 3, '3');
+    FAIL_UNLESS_EQUAL(offset, 5);
+    dynstr_free(dynstr);
+    return true;
+}
+
+
 static void setup(void)
 {
     dynstr_init();
@@ -676,6 +741,11 @@ static const struct test tests[] = {
     TEST(test_first_byte_does_not_find_nonexistent_byte),
     TEST(test_first_byte_does_not_find_byte_outside_range),
     TEST(test_first_byte_only_finds_byte_inside_range),
+    TEST(test_last_byte_finds_byte),
+    TEST(test_last_byte_only_finds_last_byte),
+    TEST(test_last_byte_does_not_find_nonexistent_byte),
+    TEST(test_last_byte_does_not_find_byte_outside_range),
+    TEST(test_last_byte_only_finds_byte_inside_range),
 };
 static const int num_tests = sizeof(tests) / sizeof(tests[0]);