Data commit

Task/Tokenize-a-string-with-escaping/C/tokenize-a-string-with-escaping.c

@@ -0,0 +1,101 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+#define STR_DEMO "one^|uno||three^^^^|four^^^|^cuatro|"
+#define SEP '|'
+#define ESC '^'
+
+typedef char* Str; /* just for an easier reading */
+
+/* ===> FUNCTION PROTOTYPES <================================================ */
+unsigned int ElQ( const char *s, char sep, char esc );
+Str *Tokenize( char *s, char sep, char esc, unsigned int *q );
+
+/*==============================================================================
+Main function.
+Just passes a copy of the STR_DEMO string to the tokenization function and shows
+the results.
+==============================================================================*/
+
+int main() {
+    char s[] = STR_DEMO;
+    unsigned int i, q;
+
+    Str *list = Tokenize( s, SEP, ESC, &q );
+
+    if( list != NULL ) {
+        printf( "\n Original string: %s\n\n", STR_DEMO );
+        printf( " %d tokens:\n\n", q );
+
+        for( i=0; i<q; ++i )
+            printf( " %4d. %s\n", i+1, list[i] );
+
+        free( list );
+    }
+
+    return 0;
+}
+
+/*==============================================================================
+"ElQ" stands for "Elements Quantity". Counts the amount of valid element in the
+string s, according to the separator character provided in sep and the escape
+character provided in esc.
+==============================================================================*/
+
+unsigned int ElQ( const char *s, char sep, char esc ) {
+    unsigned int q, e;
+    const char *p;
+
+    for( e=0, q=1, p=s; *p; ++p ) {
+        if( *p == esc )
+            e = !e;
+        else if( *p == sep )
+            q += !e;
+        else e = 0;
+    }
+
+    return q;
+}
+
+/*==============================================================================
+The actual tokenization function.
+Allocates as much dynamic memory as needed to contain the pointers to the
+tokenized portions of the string passed as the "s" parameter, then looks for the
+separators characters sep, paying attention to the occurrences of the escape
+character provided in esc. When a valid separator is found, the function swaps
+it with a '\0' terminator character and stores the pointer to the next string
+into the array of pointers in dynamic memory. On output, the value of *q is the
+number of pointers in the array. The caller is responsible for deallocating with
+free() the returned array of pointers when it is no longer needed.
+In case of failure, NULL is returned.
+==============================================================================*/
+
+Str *Tokenize( char *s, char sep, char esc, unsigned int *q ) {
+    Str *list = NULL;
+
+    *q = ElQ( s, sep, esc );
+    list = malloc( *q * sizeof(Str) );
+
+    if( list != NULL ) {
+        unsigned int e, i;
+        char *p;
+
+        i = 0;
+        list[i++] = s;
+
+        for( e=0, p=s; *p; ++p ) {
+            if( *p == esc ) {
+                e = !e;
+            }
+            else if( *p == sep && !e ) {
+                list[i++] = p+1;
+                *p = '\0';
+            }
+            else {
+                e = 0;
+            }
+        }
+    }
+
+    return list;
+}