Kstars

binfilehelper.h
1 /*
2  SPDX-FileCopyrightText: 2008 Akarsh Simha <[email protected]>
3 
4  SPDX-License-Identifier: GPL-2.0-or-later
5 */
6 
7 #pragma once
8 
9 #include <QString>
10 #include <QVector>
11 
12 #include <cstdio>
13 
14 class QString;
15 
16 /**
17  * @short A structure describing a data field in the binary file. Its size is 16 bytes.
18  */
19 typedef struct dataElement
20 {
21  char name[10] = ""; /**< Field name (eg. RA) */
22  qint8 size { 0 }; /**< Field size in bytes (eg. 4) */
23  quint8 type { 0 };
24  qint32 scale { 0 }; /**< Field scale. The final field value = raw_value * scale */
25 } dataElement;
26 
27 /**
28  * @class BinFileHelper
29  *
30  * This class provides utility functions to handle binary data files in the format prescribed
31  * by KStars. The file format is designed specifically to support data that has the form of an
32  * array of structures. See data/README.fileformat for details.
33  * The methods use primitive C file I/O routines defined in stdio.h to obtain efficiency
34  * @short Implements an interface to handle binary data files used by KStars
35  * @author Akarsh Simha
36  * @version 1.0
37  */
39 {
40  public:
41  /** Constructor */
42  BinFileHelper();
43 
44  /** Destructor */
46 
47  /**
48  * @short Checks if a file exists. WARNING: Might be incompatible in other locales
49  */
50  static bool testFileExists(const QString &fileName);
51 
52  /**
53  * WARNING: This function may not be compatible in other locales, because it calls QString::toAscii
54  * @short Open a Binary data file and set the handle
55  * @param fileName Reference to QString containing the name of the file
56  * @return Handle to the file if successful, nullptr if an error occurred, sets the error.
57  */
58 
59  FILE *openFile(const QString &fileName);
60 
61  /**
62  * @short Read the header and index table from the file and fill up the QVector s with the entries
63  * @return True if successful, false if an error occurred, sets the error.
64  */
65  bool readHeader();
66 
67  /**
68  * @short Close the binary data file
69  */
70  void closeFile();
71 
72  /**
73  * @short Get error number
74  * @return A number corresponding to the error
75  */
76  int getErrorNumber();
77 
78  /**
79  * @short Get error string
80  * @return A QString containing the error message to be displayed
81  */
82  QString getError();
83 
84  /**
85  * @short Get field by name
86  * @param fieldName Name of the field
87  * @return A dataElement structure containing field data if the field exists,
88  * containing junk values if the field doesn't exist
89  */
90  struct dataElement getField(const QString &fieldName) const;
91 
92  /**
93  * @short Check whether a field exists
94  * @param FieldName Name of the field
95  * @return True if the field exists, false if it does not or the FD hasn't been read yet
96  */
97  bool isField(const QString &FieldName) const;
98 
99  /**
100  * @short Check whether file properties are real or bogus
101  * @return The value of private variable indexUpdated, which is true if data has been updated
102  */
103  inline bool propertiesUpdated() const { return indexUpdated; }
104 
105  /**
106  * @short Get the file handle corresponding to the currently open file
107  * @return The filehandle if a file is open, nullptr if no file is open
108  */
109  inline FILE *getFileHandle() const { return fileHandle; }
110 
111  /**
112  * @short Returns the offset in the file corresponding to the given index ID
113  * @param id ID of the index entry whose offset is required
114  * @return The offset corresponding to that index ID, 0 if the index hasn't been read
115  */
116  inline long getOffset(int id) const { return (indexUpdated ? indexOffset.at(id) : 0); }
117 
118  /**
119  * @short Returns the number of records under the given index ID
120  * @param id ID of the index entry
121  * @return The number of records under index that index ID, or 0 if the index has not been read
122  */
123  inline unsigned int getRecordCount(int id) const { return (indexUpdated ? indexCount.at(id) : 0); }
124 
125  /**
126  * @short Returns the total number of records in the file
127  * @return The number of records in the file, or 0 if the index has not been read
128  */
129  inline unsigned long getRecordCount() const { return (indexUpdated ? recordCount : 0); }
130 
131  /**
132  * @short Should we do byte swapping?
133  * @note To be called only after the header has been parsed
134  * @return true if we must do byte swapping, false if not
135  */
136  inline bool getByteSwap() const { return byteswap; }
137 
138  /**
139  * @short Return a guessed record size
140  * @note The record size returned is guessed from the field descriptor table and may
141  * not be correct in many cases
142  * @return A guessed size of the record, or zero if the FD hasn't been read yet
143  */
144  inline int guessRecordSize() const { return (RSUpdated ? recordSize : 0); }
145 
146  /**
147  * @short Override record size
148  * @note To be used to override the guess in case the guess is wrong. This method should be called
149  * before calling readHeader(). Use this only if you are sure of the recordSize or are sure
150  * that the guess will not work.
151  * @param rs The correct recordSize
152  */
153  inline void setRecordSize(int rs)
154  {
155  recordSize = rs;
156  RSUpdated = true;
157  }
158 
159  /**
160  * @short Returns the number of fields as suggested by the field descriptor in the header
161  * @return Number of fields, or zero if the FD hasn't been read yet
162  */
163  inline int getFieldCount() const { return (FDUpdated ? nfields : 0); }
164 
165  /**
166  * @short Returns the header text
167  * @return QString containing the header text if header has been read, blank QString otherwise
168  */
169  inline QString getHeaderText() const { return (preambleUpdated ? headerText : ""); }
170 
171  /**
172  * @short Returns the offset at which the data begins
173  * @return The value of dataOffset if indexUpdated, else zero
174  */
175  inline long getDataOffset() const { return (indexUpdated ? dataOffset : 0); }
176 
177  /**
178  * @short Returns the offset at which the index table begins
179  * @return The value of itableOffset if FDUpdated, else zero
180  */
181  inline long getIndexTableOffset() const { return (FDUpdated ? itableOffset : 0); }
182 
183  /**
184  * @short Wrapper around fseek for large offsets
185  *
186  * fseek takes a signed long for the offset, since it can be
187  * either positive or negative. If the argument is a 32-bit
188  * unsigned integer, fseek will fail in most situations, since
189  * that will be interpreted as a number of the opposite sign.
190  * This wrapper circumvents that problem by repeatedly calling
191  * fseek twice if the offset is too large. Useful when 64-bit
192  * handling is really not necessary.
193  *
194  * @return Zero on success. Else, error code of the first failing fseek call.
195  * @note Clearly, this method can move forward only. When we need
196  * one that goes back, we'll implement that.
197  */
198  static int unsigned_KDE_fseek(FILE *stream, quint32 offset, int whence);
199 
200  /*! @short An enum providing user-friendly names for errors encountered */
201  enum Errors
202  {
203  ERR_NULL, /*!< No error occurred */
204  ERR_FILEOPEN, /*!< File could not be opened */
205  ERR_FD_TRUNC, /*!< Field descriptor table is truncated */
206  ERR_INDEX_TRUNC, /*!< File ends prematurely, before expected end of index table */
207  ERR_INDEX_BADID, /*!< Index table has an invalid ID entry */
208  ERR_INDEX_IDMISMATCH, /*!< Index table has a mismatched ID entry [ID found in the wrong place] */
209  ERR_INDEX_BADOFFSET, /*!< Offset / Record count specified in the Index table is bad */
210  ERR_BADSEEK /*!< Premature end of file / bad seek while reading index table */
211  };
212 
213  private:
214  /**
215  * @short Backends for readHeader without cleanup on abort
216  * @return Return the appropriate error code, or ERR_NULL if successful
217  */
218  enum Errors __readHeader();
219 
220  /**
221  * @short Helper function that clears all field entries in the QVector fields
222  */
223  void clearFields();
224 
225  /**
226  * @short Helper function that sets all variables to their initial values
227  */
228  void init();
229 
230  /// Handle to the file.
231  FILE *fileHandle { nullptr};
232  /// Stores offsets corresponding to each index table entry
233  QVector<unsigned long> indexOffset;
234  /// Stores number of records under each index table entry
235  QVector<unsigned int> indexCount;
236  /// True if the data from the index, and associated properties have been updated
237  bool indexUpdated { false };
238  /// True if the data from the Field Descriptor, and associated properties have been updated
239  bool FDUpdated { false };
240  /// True if the recordSize parameter is set correctly, either manually or bye reading the FD
241  bool RSUpdated { false };
242  /// True if the data from the preamble and associated properties have been updated
243  bool preambleUpdated { false };
244  /// Stores the number corresponding to the previous error
245  enum Errors errnum { ERR_NULL };
246  /// True if byteswapping should be done
247  bool byteswap { false };
248  /// Stores the size of a record in bytes for quick retrieval
249  int recordSize { 0 };
250  /// Maintains a list of fields in the file, along with relevant details
251  QVector<dataElement *> fields;
252  /// Stores the file header text
253  QString headerText;
254  /// Stores the number of fields as indicated by the field descriptor
255  qint16 nfields { 0 };
256  /// Stores the size of the index table in number of entries
257  quint32 indexSize { 0 };
258  /// Stores the offset position of the first index table entry
259  long itableOffset { 0 };
260  /// Stores the offset position of the start of data
261  long dataOffset { 0 };
262  /// Stores the most recent 'unread' error message
263  QString errorMessage;
264  /// Stores the total number of records in the file
265  unsigned long recordCount { 0 };
266  /// Stores the version number of the file
267  quint8 versionNumber { 0 };
268 };
int guessRecordSize() const
Return a guessed record size.
static int unsigned_KDE_fseek(FILE *stream, quint32 offset, int whence)
Wrapper around fseek for large offsets.
bool propertiesUpdated() const
Check whether file properties are real or bogus.
FILE * getFileHandle() const
Get the file handle corresponding to the currently open file.
static bool testFileExists(const QString &fileName)
Checks if a file exists.
bool readHeader()
Read the header and index table from the file and fill up the QVector s with the entries.
int getFieldCount() const
Returns the number of fields as suggested by the field descriptor in the header.
bool getByteSwap() const
Should we do byte swapping?
~BinFileHelper()
Destructor.
void setRecordSize(int rs)
Override record size.
bool isField(const QString &FieldName) const
Check whether a field exists.
void closeFile()
Close the binary data file.
unsigned int getRecordCount(int id) const
Returns the number of records under the given index ID.
QString getError()
Get error string.
const T & at(int i) const const
long getOffset(int id) const
Returns the offset in the file corresponding to the given index ID.
Errors
An enum providing user-friendly names for errors encountered.
struct dataElement getField(const QString &fieldName) const
Get field by name.
Implements an interface to handle binary data files used by KStars.
Definition: binfilehelper.h:38
char name[10]
Field name (eg.
Definition: binfilehelper.h:21
unsigned long getRecordCount() const
Returns the total number of records in the file.
qint8 size
Field size in bytes (eg.
Definition: binfilehelper.h:22
A structure describing a data field in the binary file.
Definition: binfilehelper.h:19
long getIndexTableOffset() const
Returns the offset at which the index table begins.
BinFileHelper()
Constructor.
qint32 scale
Field scale.
Definition: binfilehelper.h:24
FILE * openFile(const QString &fileName)
WARNING: This function may not be compatible in other locales, because it calls QString::toAscii.
long getDataOffset() const
Returns the offset at which the data begins.
int getErrorNumber()
Get error number.
QString getHeaderText() const
Returns the header text.
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