Diff: SD.cpp

Revision:

0:405b46e831df

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SD.cpp	Tue Jul 14 01:58:28 2015 +0000
@@ -0,0 +1,616 @@
+/*
+
+ SD - a slightly more friendly wrapper for sdfatlib
+
+ This library aims to expose a subset of SD card functionality
+ in the form of a higher level "wrapper" object.
+
+ License: GNU General Public License V3
+          (Because sdfatlib is licensed with this.)
+
+ (C) Copyright 2010 SparkFun Electronics
+
+
+ This library provides four key benefits:
+
+   * Including `SD.h` automatically creates a global
+     `SD` object which can be interacted with in a similar
+     manner to other standard global objects like `Serial` and `Ethernet`.
+
+   * Boilerplate initialisation code is contained in one method named 
+     `begin` and no further objects need to be created in order to access
+     the SD card.
+
+   * Calls to `open` can supply a full path name including parent 
+     directories which simplifies interacting with files in subdirectories.
+
+   * Utility methods are provided to determine whether a file exists
+     and to create a directory heirarchy.
+
+
+  Note however that not all functionality provided by the underlying
+  sdfatlib library is exposed.
+
+ */
+
+/*
+
+  Implementation Notes
+
+  In order to handle multi-directory path traversal, functionality that 
+  requires this ability is implemented as callback functions.
+
+  Individual methods call the `walkPath` function which performs the actual
+  directory traversal (swapping between two different directory/file handles
+  along the way) and at each level calls the supplied callback function.
+
+  Some types of functionality will take an action at each level (e.g. exists
+  or make directory) which others will only take an action at the bottom
+  level (e.g. open).
+
+ */
+
+#include "SD.h"
+
+// Used by `getNextPathComponent`
+#define MAX_COMPONENT_LEN 12 // What is max length?
+#define PATH_COMPONENT_BUFFER_LEN MAX_COMPONENT_LEN+1
+
+bool getNextPathComponent(char *path, unsigned int *p_offset,
+			  char *buffer) {
+  /*
+
+    Parse individual path components from a path.
+
+      e.g. after repeated calls '/foo/bar/baz' will be split
+           into 'foo', 'bar', 'baz'.
+
+    This is similar to `strtok()` but copies the component into the
+    supplied buffer rather than modifying the original string.
+
+
+    `buffer` needs to be PATH_COMPONENT_BUFFER_LEN in size.
+
+    `p_offset` needs to point to an integer of the offset at
+    which the previous path component finished.
+
+    Returns `true` if more components remain.
+
+    Returns `false` if this is the last component.
+      (This means path ended with 'foo' or 'foo/'.)
+
+   */
+
+  // TODO: Have buffer local to this function, so we know it's the
+  //       correct length?
+
+  int bufferOffset = 0;
+
+  int offset = *p_offset;
+
+  // Skip root or other separator
+  if (path[offset] == '/') {
+    offset++;
+  }
+  
+  // Copy the next next path segment
+  while (bufferOffset < MAX_COMPONENT_LEN
+	 && (path[offset] != '/')
+	 && (path[offset] != '\0')) {
+    buffer[bufferOffset++] = path[offset++];
+  }
+
+  buffer[bufferOffset] = '\0';
+
+  // Skip trailing separator so we can determine if this
+  // is the last component in the path or not.
+  if (path[offset] == '/') {
+    offset++;
+  }
+
+  *p_offset = offset;
+
+  return (path[offset] != '\0');
+}
+
+
+
+boolean walkPath(char *filepath, SdFile& parentDir,
+		 boolean (*callback)(SdFile& parentDir,
+				     char *filePathComponent,
+				     boolean isLastComponent,
+				     void *object),
+		 void *object = NULL) {
+  /*
+     
+     When given a file path (and parent directory--normally root),
+     this function traverses the directories in the path and at each
+     level calls the supplied callback function while also providing
+     the supplied object for context if required.
+
+       e.g. given the path '/foo/bar/baz'
+            the callback would be called at the equivalent of
+	    '/foo', '/foo/bar' and '/foo/bar/baz'.
+
+     The implementation swaps between two different directory/file
+     handles as it traverses the directories and does not use recursion
+     in an attempt to use memory efficiently.
+
+     If a callback wishes to stop the directory traversal it should
+     return false--in this case the function will stop the traversal,
+     tidy up and return false.
+
+     If a directory path doesn't exist at some point this function will
+     also return false and not subsequently call the callback.
+
+     If a directory path specified is complete, valid and the callback
+     did not indicate the traversal should be interrupted then this
+     function will return true.
+
+   */
+
+
+  SdFile subfile1;
+  SdFile subfile2;
+
+  char buffer[PATH_COMPONENT_BUFFER_LEN]; 
+
+  unsigned int offset = 0;
+
+  SdFile *p_parent;
+  SdFile *p_child;
+
+  SdFile *p_tmp_sdfile;  
+  
+  p_child = &subfile1;
+  
+  p_parent = &parentDir;
+
+  while (true) {
+
+    boolean moreComponents = getNextPathComponent(filepath, &offset, buffer);
+
+    boolean shouldContinue = callback((*p_parent), buffer, !moreComponents, object);
+
+    if (!shouldContinue) {
+      // TODO: Don't repeat this code?
+      // If it's one we've created then we
+      // don't need the parent handle anymore.
+      if (p_parent != &parentDir) {
+        (*p_parent).close();
+      }
+      return false;
+    }
+    
+    if (!moreComponents) {
+      break;
+    }
+    
+    boolean exists = (*p_child).open(*p_parent, buffer, O_RDONLY);
+
+    // If it's one we've created then we
+    // don't need the parent handle anymore.
+    if (p_parent != &parentDir) {
+      (*p_parent).close();
+    }
+    
+    // Handle case when it doesn't exist and we can't continue...
+    if (exists) {
+      // We alternate between two file handles as we go down
+      // the path.
+      if (p_parent == &parentDir) {
+        p_parent = &subfile2;
+      }
+
+      p_tmp_sdfile = p_parent;
+      p_parent = p_child;
+      p_child = p_tmp_sdfile;
+    } else {
+      return false;
+    }
+  }
+  
+  if (p_parent != &parentDir) {
+    (*p_parent).close(); // TODO: Return/ handle different?
+  }
+
+  return true;
+}
+
+
+
+/*
+
+   The callbacks used to implement various functionality follow.
+
+   Each callback is supplied with a parent directory handle,
+   character string with the name of the current file path component,
+   a flag indicating if this component is the last in the path and
+   a pointer to an arbitrary object used for context.
+
+ */
+
+boolean callback_pathExists(SdFile& parentDir, char *filePathComponent, 
+			    boolean isLastComponent, void *object) {
+  /*
+
+    Callback used to determine if a file/directory exists in parent
+    directory.
+
+    Returns true if file path exists.
+
+  */
+  SdFile child;
+
+  boolean exists = child.open(parentDir, filePathComponent, O_RDONLY);
+  
+  if (exists) {
+     child.close(); 
+  }
+  
+  return exists;
+}
+
+
+
+boolean callback_makeDirPath(SdFile& parentDir, char *filePathComponent, 
+			     boolean isLastComponent, void *object) {
+  /*
+
+    Callback used to create a directory in the parent directory if
+    it does not already exist.
+
+    Returns true if a directory was created or it already existed.
+
+  */
+  boolean result = false;
+  SdFile child;
+  
+  result = callback_pathExists(parentDir, filePathComponent, isLastComponent, object);
+  if (!result) {
+    result = child.makeDir(parentDir, filePathComponent);
+  } 
+  
+  return result;
+}
+
+
+  /*
+
+boolean callback_openPath(SdFile& parentDir, char *filePathComponent, 
+			  boolean isLastComponent, void *object) {
+
+    Callback used to open a file specified by a filepath that may
+    specify one or more directories above it.
+
+    Expects the context object to be an instance of `SDClass` and
+    will use the `file` property of the instance to open the requested
+    file/directory with the associated file open mode property.
+
+    Always returns true if the directory traversal hasn't reached the
+    bottom of the directory heirarchy.
+
+    Returns false once the file has been opened--to prevent the traversal
+    from descending further. (This may be unnecessary.)
+
+  if (isLastComponent) {
+    SDClass *p_SD = static_cast<SDClass*>(object);
+    p_SD->file.open(parentDir, filePathComponent, p_SD->fileOpenMode);
+    if (p_SD->fileOpenMode == FILE_WRITE) {
+      p_SD->file.seekSet(p_SD->file.fileSize());
+    }
+    // TODO: Return file open result?
+    return false;
+  }
+  return true;
+}
+  */
+
+
+
+boolean callback_remove(SdFile& parentDir, char *filePathComponent, 
+			boolean isLastComponent, void *object) {
+  if (isLastComponent) {
+    return SdFile::remove(parentDir, filePathComponent);
+  }
+  return true;
+}
+
+boolean callback_rmdir(SdFile& parentDir, char *filePathComponent, 
+			boolean isLastComponent, void *object) {
+  if (isLastComponent) {
+    SdFile f;
+    if (!f.open(parentDir, filePathComponent, O_READ)) return false;
+    return f.rmDir();
+  }
+  return true;
+}
+
+
+
+/* Implementation of class used to create `SDCard` object. */
+
+
+
+boolean SDClass::begin(uint8_t csPin) {
+  /*
+
+    Performs the initialisation required by the sdfatlib library.
+
+    Return true if initialization succeeds, false otherwise.
+
+   */
+  return card.init(SPI_HALF_SPEED, csPin) &&
+         volume.init(card) &&
+         root.openRoot(volume);
+}
+
+
+
+// this little helper is used to traverse paths
+SdFile SDClass::getParentDir(const char *filepath, int *index) {
+  // get parent directory
+  SdFile d1 = root; // start with the mostparent, root!
+  SdFile d2;
+
+  // we'll use the pointers to swap between the two objects
+  SdFile *parent = &d1;
+  SdFile *subdir = &d2;
+  
+  const char *origpath = filepath;
+
+  while (strchr(filepath, '/')) {
+
+    // get rid of leading /'s
+    if (filepath[0] == '/') {
+      filepath++;
+      continue;
+    }
+    
+    if (! strchr(filepath, '/')) {
+      // it was in the root directory, so leave now
+      break;
+    }
+
+    // extract just the name of the next subdirectory
+    uint8_t idx = strchr(filepath, '/') - filepath;
+    if (idx > 12)
+      idx = 12;    // dont let them specify long names
+    char subdirname[13];
+    strncpy(subdirname, filepath, idx);
+    subdirname[idx] = 0;
+
+    // close the subdir (we reuse them) if open
+    subdir->close();
+    if (! subdir->open(parent, subdirname, O_READ)) {
+      // failed to open one of the subdirectories
+      return SdFile();
+    }
+    // move forward to the next subdirectory
+    filepath += idx;
+
+    // we reuse the objects, close it.
+    parent->close();
+
+    // swap the pointers
+    SdFile *t = parent;
+    parent = subdir;
+    subdir = t;
+  }
+
+  *index = (int)(filepath - origpath);
+  // parent is now the parent diretory of the file!
+  return *parent;
+}
+
+
+File SDClass::open(const char *filepath, uint8_t mode) {
+  /*
+
+     Open the supplied file path for reading or writing.
+
+     The file content can be accessed via the `file` property of
+     the `SDClass` object--this property is currently
+     a standard `SdFile` object from `sdfatlib`.
+
+     Defaults to read only.
+
+     If `write` is true, default action (when `append` is true) is to
+     append data to the end of the file.
+
+     If `append` is false then the file will be truncated first.
+
+     If the file does not exist and it is opened for writing the file
+     will be created.
+
+     An attempt to open a file for reading that does not exist is an
+     error.
+
+   */
+
+  int pathidx;
+
+  // do the interative search
+  SdFile parentdir = getParentDir(filepath, &pathidx);
+  // no more subdirs!
+
+  filepath += pathidx;
+
+  if (! filepath[0]) {
+    // it was the directory itself!
+    return File(parentdir, "/");
+  }
+
+  // Open the file itself
+  SdFile file;
+
+  // failed to open a subdir!
+  if (!parentdir.isOpen())
+    return File();
+
+  // there is a special case for the Root directory since its a static dir
+  if (parentdir.isRoot()) {
+    if ( ! file.open(SD.root, filepath, mode)) {
+      // failed to open the file :(
+      return File();
+    }
+    // dont close the root!
+  } else {
+    if ( ! file.open(parentdir, filepath, mode)) {
+      return File();
+    }
+    // close the parent
+    parentdir.close();
+  }
+
+  if (mode & (O_APPEND | O_WRITE)) 
+    file.seekSet(file.fileSize());
+  return File(file, filepath);
+}
+
+
+/*
+File SDClass::open(char *filepath, uint8_t mode) {
+  //
+
+     Open the supplied file path for reading or writing.
+
+     The file content can be accessed via the `file` property of
+     the `SDClass` object--this property is currently
+     a standard `SdFile` object from `sdfatlib`.
+
+     Defaults to read only.
+
+     If `write` is true, default action (when `append` is true) is to
+     append data to the end of the file.
+
+     If `append` is false then the file will be truncated first.
+
+     If the file does not exist and it is opened for writing the file
+     will be created.
+
+     An attempt to open a file for reading that does not exist is an
+     error.
+
+   //
+
+  // TODO: Allow for read&write? (Possibly not, as it requires seek.)
+
+  fileOpenMode = mode;
+  walkPath(filepath, root, callback_openPath, this);
+
+  return File();
+
+}
+*/
+
+
+//boolean SDClass::close() {
+//  /*
+//
+//    Closes the file opened by the `open` method.
+//
+//   */
+//  file.close();
+//}
+
+
+boolean SDClass::exists(char *filepath) {
+  /*
+
+     Returns true if the supplied file path exists.
+
+   */
+  return walkPath(filepath, root, callback_pathExists);
+}
+
+
+//boolean SDClass::exists(char *filepath, SdFile& parentDir) {
+//  /*
+//
+//     Returns true if the supplied file path rooted at `parentDir`
+//     exists.
+//
+//   */
+//  return walkPath(filepath, parentDir, callback_pathExists);
+//}
+
+
+boolean SDClass::mkdir(char *filepath) {
+  /*
+  
+    Makes a single directory or a heirarchy of directories.
+
+    A rough equivalent to `mkdir -p`.
+  
+   */
+  return walkPath(filepath, root, callback_makeDirPath);
+}
+
+boolean SDClass::rmdir(char *filepath) {
+  /*
+  
+    Makes a single directory or a heirarchy of directories.
+
+    A rough equivalent to `mkdir -p`.
+  
+   */
+  return walkPath(filepath, root, callback_rmdir);
+}
+
+boolean SDClass::remove(char *filepath) {
+  return walkPath(filepath, root, callback_remove);
+}
+
+
+// allows you to recurse into a directory
+File File::openNextFile(uint8_t mode) {
+  dir_t p;
+
+  //Serial.print("\t\treading dir...");
+  while (_file->readDir(&p) > 0) {
+
+    // done if past last used entry
+    if (p.name[0] == DIR_NAME_FREE) {
+      //Serial.println("end");
+      return File();
+    }
+
+    // skip deleted entry and entries for . and  ..
+    if (p.name[0] == DIR_NAME_DELETED || p.name[0] == '.') {
+      //Serial.println("dots");
+      continue;
+    }
+
+    // only list subdirectories and files
+    if (!DIR_IS_FILE_OR_SUBDIR(&p)) {
+      //Serial.println("notafile");
+      continue;
+    }
+
+    // print file name with possible blank fill
+    SdFile f;
+    char name[13];
+    _file->dirName(p, name);
+    //Serial.print("try to open file ");
+    //Serial.println(name);
+
+    if (f.open(_file, name, mode)) {
+      //Serial.println("OK!");
+      return File(f, name);    
+    } else {
+      //Serial.println("ugh");
+      return File();
+    }
+  }
+
+  //Serial.println("nothing");
+  return File();
+}
+
+void File::rewindDirectory(void) {  
+  if (isDirectory())
+    _file->rewind();
+}
+
+SDClass SD;