SD.cpp

/*

  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 hierarchy.


  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"

namespace SDLib {

// Used by `getNextPathComponent`
#define MAX_COMPONENT_LEN 12
#define PATH_COMPONENT_BUFFER_LEN (MAX_COMPONENT_LEN + 1)
// BASENAME:char(8) + '.':char(1) + EXT:char(3) = 12 (a.k.a short 8.3 name)
// And an extra space for '\0' for path buffer

  bool getNextPathComponent(const 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');
  }



  bool walkPath(const char *filepath, SdFile& parentDir,
                bool(*callback)(SdFile& parentDir,
                                const char *filePathComponent,
                                bool 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) {

      bool moreComponents = getNextPathComponent(filepath, &offset, buffer);

      bool 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;
      }

      bool 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.

  */

  bool callback_pathExists(SdFile& parentDir, const char *filePathComponent,
                           bool /* isLastComponent */, void * /* object */) {
    /*

      Callback used to determine if a file/directory exists in parent
      directory.

      Returns true if file path exists.

    */
    SdFile child;

    bool exists = child.open(parentDir, filePathComponent, O_RDONLY);

    if (exists) {
      child.close();
    }

    return exists;
  }



  bool callback_makeDirPath(SdFile& parentDir, const char *filePathComponent,
                            bool 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.

    */
    bool result = false;
    SdFile child;

    result = callback_pathExists(parentDir, filePathComponent, isLastComponent, object);
    if (!result) {
      result = child.makeDir(parentDir, filePathComponent);
    }

    return result;
  }


  /*

    bool callback_openPath(SdFile& parentDir, char *filePathComponent,
  	  bool 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 hierarchy.

    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;
    }
  */



  bool callback_remove(SdFile& parentDir, const char *filePathComponent,
                       bool isLastComponent, void * /* object */) {
    if (isLastComponent) {
      return SdFile::remove(parentDir, filePathComponent);
    }
    return true;
  }

  bool callback_rmdir(SdFile& parentDir, const char *filePathComponent,
                      bool 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. */



  bool SDClass::begin(uint8_t csPin) {
    if (root.isOpen()) {
      root.close();
    }

    /*

      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);
  }
#ifndef SOFTWARE_SPI //Added compiler directive so that MEGA works with this code
  bool SDClass::begin(uint32_t clock, uint8_t csPin) {
    if (root.isOpen()) {
      root.close();
    }

    return card.init(SPI_HALF_SPEED, csPin) &&
           card.setSpiClock(clock) &&
           volume.init(card) &&
           root.openRoot(volume);
  }
#else
  bool SDClass::begin(uint32_t clock, uint8_t csPin) {
    if (root.isOpen()) {
      root.close();
    }

    return card.init(SPI_HALF_SPEED, csPin) &&
           card.setSpiClock(clock) &&
           volume.init(card) &&
           root.openRoot(volume);
  }
#endif  //SOFTWARE_SPI
  
  //call this when a card is removed. It will allow you to insert and initialise a new card.
  void SDClass::end() {
    root.close();
  }

  // this little helper is used to traverse paths
  SdFile SDClass::getParentDir(const char *filepath, int *index) {
    // get parent directory
    SdFile d1;
    SdFile d2;

    d1.openRoot(volume); // start with the mostparent, root!

    // 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;  // don't 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 directory 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 interactive 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();
    }

    if (! file.open(parentdir, filepath, mode)) {
      return File();
    }
    // close the parent
    parentdir.close();

    if ((mode & (O_APPEND | O_WRITE)) == (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();

    }
  */


  //bool SDClass::close() {
  //  /*
  //
  //    Closes the file opened by the `open` method.
  //
  //   */
  //  file.close();
  //}


  bool SDClass::exists(const char *filepath) {
    /*

       Returns true if the supplied file path exists.

    */
    return walkPath(filepath, root, callback_pathExists);
  }


  //bool SDClass::exists(char *filepath, SdFile& parentDir) {
  //  /*
  //
  //     Returns true if the supplied file path rooted at `parentDir`
  //     exists.
  //
  //   */
  //  return walkPath(filepath, parentDir, callback_pathExists);
  //}


  bool SDClass::mkdir(const char *filepath) {
    /*

      Makes a single directory or a hierarchy of directories.

      A rough equivalent to `mkdir -p`.

    */
    return walkPath(filepath, root, callback_makeDirPath);
  }

  bool SDClass::rmdir(const char *filepath) {
    /*

      Remove a single directory or a hierarchy of directories.

      A rough equivalent to `rm -rf`.

    */
    return walkPath(filepath, root, callback_rmdir);
  }

  bool SDClass::remove(const 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;

};