refactor utils.h and implement simple_compressionCCtx.c

examples/utils.h

@@ -9,7 +9,7 @@
  */
 
 /*
- * This header file has common utility functions used in examples. 
+ * This header file has common utility functions used in examples.
  */
 #ifndef UTILS_H
 #define UTILS_H
@@ -21,7 +21,7 @@
 #include <sys/stat.h>  // stat
 
 /*
- * Define the returned error code from utility functions. 
+ * Define the returned error code from utility functions.
  */
 typedef enum {
     ERROR_fsize = 1,
@@ -35,21 +35,33 @@ typedef enum {
     ERROR_largeFile = 9,
 } UTILS_ErrorCode;
 
-/*! fsize_orDie() : 
+/*! fsize_orDie() :
  * Get the size of a given file path.
- * 
+ *
  * @return The size of a given file path.
  */
-static off_t fsize_orDie(const char *filename)
+static size_t fsize_orDie(const char *filename)
 {
     struct stat st;
-    if (stat(filename, &st) == 0) return st.st_size;
-    /* error */
-    perror(filename);
-    exit(ERROR_fsize);
+    if (stat(filename, &st) != 0) {
+        /* error */
+        perror(filename);
+        exit(ERROR_fsize);
+    }
+
+    off_t const fileSize = st.st_size;
+    size_t const size = (size_t)fileSize;
+    /* if off_t -> size_t conversion causes discrepancy, the file size is
+     * too big for at least 1 type to handle
+     */
+    if (size != fileSize) {   /* narrowcast overflow */
+        fprintf(stderr, "%s : filesize too large \n", filename);
+        exit(ERROR_largeFile);
+    }
+    return size;
 }
 
-/*! fopen_orDie() : 
+/*! fopen_orDie() :
  * Open a file using given file path and open option.
  *
  * @return If successful this function will return a FILE pointer to an
@@ -64,7 +76,7 @@ static FILE* fopen_orDie(const char *filename, const char *instruction)
     exit(ERROR_fopen);
 }
 
-/*! fclose_orDie() : 
+/*! fclose_orDie() :
  * Close an opened file using given FILE pointer.
  */
 static void fclose_orDie(FILE* file)
@@ -75,11 +87,11 @@ static void fclose_orDie(FILE* file)
     exit(ERROR_fclose);
 }
 
-/*! fread_orDie() : 
- * 
+/*! fread_orDie() :
+ *
  * Read sizeToRead bytes from a given file, storing them at the
  * location given by buffer.
- * 
+ *
  * @return The number of bytes read.
  */
 static size_t fread_orDie(void* buffer, size_t sizeToRead, FILE* file)
@@ -93,12 +105,12 @@ static size_t fread_orDie(void* buffer, size_t sizeToRead, FILE* file)
 }
 
 /*! fwrite_orDie() :
- *  
+ *
  * Write sizeToWrite bytes to a file pointed to by file, obtaining
  * them from a location given by buffer.
  *
  * Note: This function will send an error to stderr and exit if it
- * cannot write data to the given file pointer. 
+ * cannot write data to the given file pointer.
  *
  * @return The number of bytes written.
  */
@@ -113,7 +125,7 @@ static size_t fwrite_orDie(const void* buffer, size_t sizeToWrite, FILE* file)
 
 /*! malloc_orDie() :
  * Allocate memory.
- * 
+ *
  * @return If successful this function returns a pointer to allo-
  * cated memory.  If there is an error, this function will send that
  * error to stderr and exit.
@@ -128,39 +140,41 @@ static void* malloc_orDie(size_t size)
 }
 
 /*! loadFile_orDie() :
- * Read size bytes from a file.
- * 
+ * Read size bytes from a file. If buffer is not provided (i.e., buffer == null),
+ * malloc will be called to allocate one.
+ *
  * Note: This function will send an error to stderr and exit if it
  * cannot read data from the given file path.
- * 
+ *
  * @return If successful this function will return a pointer to read
  * data otherwise it will printout an error to stderr and exit.
  */
-static void* loadFile_orDie(const char* fileName, size_t* size)
+static void* loadFile_orDie(const char* fileName, size_t* size, void* buffer, int bufferSize)
 {
-    off_t const fileSize = fsize_orDie(fileName);
-    size_t const buffSize = (size_t)fileSize;
-    if ((off_t)buffSize < fileSize) {   /* narrowcast overflow */
-        fprintf(stderr, "%s : filesize too large \n", fileName);
-        exit(ERROR_largeFile);
-    }
+    size_t const fileSize = fsize_orDie(fileName);
     FILE* const inFile = fopen_orDie(fileName, "rb");
-    void* const buffer = malloc_orDie(buffSize);
-    size_t const readSize = fread(buffer, 1, buffSize, inFile);
-    if (readSize != (size_t)buffSize) {
+    if (!buffer) {
+        buffer = malloc_orDie(fileSize);
+    }
+    else if (bufferSize < fileSize) {
+        fprintf(stderr, "%s : filesize bigger than provided buffer.\n", fileName);
+
+    }
+    size_t const readSize = fread(buffer, 1, fileSize, inFile);
+    if (readSize != (size_t)fileSize) {
         fprintf(stderr, "fread: %s : %s \n", fileName, strerror(errno));
         exit(ERROR_fread);
     }
     fclose(inFile);  /* can't fail, read only */
-    *size = buffSize;
+    *size = fileSize;
     return buffer;
 }
 
 /*! saveFile_orDie() :
- *  
+ *
  * Save buffSize bytes to a given file path, obtaining them from a location pointed
  * to by buff.
- * 
+ *
  * Note: This function will send an error to stderr and exit if it
  * cannot write to a given file.
  */