Move purely string-manipulation function to a separate file

Signed-off-by: Pradana AUMARS <paumars@courrier.dev>

src/Makefile.am

@@ -4,5 +4,7 @@ libeasycsv_la_SOURCES = \
 	easycsv_error.h \
 	easycsv_error.c \
 	easycsv_p.h \
-	easycsv_p.c
+	easycsv_p.c \
+	easycsv_string.h \
+	easycsv_string.c
 include_HEADERS = ../include/easycsv.h

src/easycsv_string.c

@@ -0,0 +1,67 @@
+#include <string.h>
+#include <stdlib.h>
+
+#include "string.h"
+
+char*
+easycsv_set_charp_to_value(const char *rowstr,
+			   unsigned int col)
+{
+  /* Get first occurance of comma in str, the first value is ommited but not the comma */
+  char *pch = (char*) rowstr;
+  /* Repeat until desired col is found */
+  for (unsigned int i = 1; i < col; i++) {
+    pch = strpbrk(pch + 1, ",");
+  }
+
+  return pch;
+}
+
+char*
+easycsv_insert_string_row(const char* val,
+			  const char* rowstr,
+			  unsigned int col,
+			  unsigned int col_max)
+{
+  size_t rowstrst = strlen(rowstr);
+  size_t st = 0;
+  size_t commas = 0;
+  char *pch = NULL;
+  char *newstr = NULL;
+
+  /* column is within limit */
+  if (1 <= col && col <= col_max) {
+
+    /* Set pch to start of value in rowstr */
+    pch = easycsv_set_charp_to_value(rowstr, col);
+
+    /* Calculate size of existing value */
+    st = strcspn(pch, ",");
+    
+    newstr = malloc(rowstrst - st + strlen(val) + 1);
+
+    /* Copy char to newstr before value (pch) */
+    strncpy(newstr, rowstr, pch - rowstr);
+
+    strcat(newstr, val);
+
+    /* Set pch to after value */
+    pch = strchr(rowstr, ',');
+
+    /* Calculate length of rest of string */
+    st = strlen(pch);
+
+    /* Concentate rest of string including NULL char */
+    strcat(newstr, pch);
+  }
+  else {
+    commas = col - col_max;
+    // csv->cols = col;
+    newstr = malloc(rowstrst + commas + strlen(val) + 1);
+    strncpy(newstr, rowstr, rowstrst);
+    for (size_t i = 0; i < commas; i++)
+      strncat(newstr, ",", 1);
+    strcat(newstr, val); // append \0
+  }
+  return newstr;
+}

src/easycsv_string.h

@@ -0,0 +1,32 @@
+#ifndef EASYCSV_STRING_P_H
+#define EASYCSV_STRING_P_H
+
+/**
+ * Returns char pointer towards the n-th occurence of ',' in a given string 
+ * This function does not check parameters!
+ * This function does not produce errors!
+ * @param[in] string of row (string with multiple occurences of ',')
+ * @param[in] n-th occurence to place the char pointer
+ * @return char pointer towards the n-th occurence of ',' in a given string
+*/
+char*
+easycsv_set_charp_to_value(const char*,
+  			   unsigned int);
+
+/**
+ * Insert a string in a comma-separated string of sub-strings in a specified position (by comma)
+ * @param[in] string to be inserted
+ * @param[in] comma-separated string
+ * @param[in] specified position of string
+ * @param[in] total number of sub-strings BEFORE manipulation
+ * @return heap-allocated string
+ */
+char*
+easycsv_insert_string_row(const char*,
+			  const char*,
+			  unsigned int,
+			  unsigned int);
+
+
+
+#endif