Decoded: OpenTTD (2003) v1.8 (2018)
Source file: smallmatrix_type.hpp
Line-by-line code walkthrough by MaiZure

smallmatrix_type.hpp defines SmallMatrix container 

Original code:
https://github.com/MaiZure/OpenTTD-1.8/blob/master/src/core/smallmatrix_type.hpp





1     COMMENT (*)
2     BLANK (-)
3     *
4     *
5     *
6     *
7     *
8     *
9     -
10    *
11    -
12    Header guard
13    Header guard
14    -
15    Include the OpenTTD type-safe memory allocation functions
16    Include the OpenTTD type-safe memory access functions
17    -
18    *
19    *
20    *
21    *
22    *
23    *
24    *
25    *
26    *
27    *
28    *
29    *
30    *
31    *
32    *
33    *
34    *
35    *
36    *
37    *
38    *
39    Sets up a class template with a type parameter
40    BLOCK START - SmallMatrix, a lightweight rectangular matrix
41    Beings the protected section of SmallMatrix
42    Data pointer to the first item
43    The width of a matrix
44    The height of the matrix
45    The total space in the matrix
46    *
47    Begins the public section of SmallMatrix
48    *
49    Default SmallMatrix constructor with init list for an empty matrix
50    *
51    *
52    *
53    *
54    *
55    Defines a copy constructor with empty initialization
56    BLOCK START - SmallMatrix copy constructor
57    Assigns the input matrix
58    BLOCK END - SmallMatrix copy constructor
59    -
60    Defines the destructor
61    BLOCK START - SmallMatrix destructor
62    Free the data
63    BLOCK END - SmallMatrix destructor
64    -
65    *
66    *
67    *
68    *
69    Defines overloaded assignment operator for SmallMatrix
70    BLOCK START - SmallMatrix = operator overload
71    Assigns the input matix to this matrix
72    Returns the pointer to self
73    BLOCK END - SmallMatrix = operator overload
74    -
75    *
76    *
77    *
78    Defines SmallMatrix::Assign with one argument, an input matrix
79    BLOCK START - SmallMatrix::Assign
80    If this is the same matrix, no need to assign so return
81    -
82    Match this matrix height to input matrix height
83    Match this matrix width to input matrix width
84    Get the number of items in the updated matrix
85    If the number of items is beyond capacity (it grew)
86    Update the capacity to the new size
87    Remove existing data
88    Allocate space for the new data
89    Copy the data from the input matrix
90    Otherwise there is enough capacity already..
91    Copy the data from the input matrix
92    End check for matrix capacity
93    BLOCK END - SmallMatrix::Assign
94    -
95    *
96    *
97    *
98    Defines SmallMatrix::Clear with no arguments
99    BLOCK START - SmallMatrix::Clear, removes all rows
100   *
101   *
102   *
103   Sets matrix width to zero
104   BLOCK END - SmallMatrix::Clear
105   -
106   *
107   *
108   *
109   Defines SmallMatrix::Reset with no arguments
110   BLOCK START - SmallMatrix::Reset
111   Removes all rows
112   Removes all columns
113   Removes entry count
114   Destroys data
115   Removes data pointer
116   BLOCK END - SmallMatrix::Reset
117   -
118   *
119   *
120   *
121   Defines SmallMatrix::Compact with no arguments
122   BLOCK START - SmallMatrix::Compant
123   Recalculates matrix capacity
124   If the new capacity is larger than the actual capacity
125   Update the actual capacity
126   Resize matrix data
127   BLOCK END - SmallMatrix::Compact
128   -
129   *
130   *
131   *
132   *
133   Defines SmallMatrix::EraseColumn with one argument: column position
134   BLOCK START - SmallMatrix::EraseColumn
135   Decrement column count and if the column wasn't the last one...
136   Copy all the proceeding data to the replaced position...
137   ..from the original position..
138   ...and get all the data
139   End check for data to move
140   BLOCK END - SmallMatrix::EraseColumn
141   -
142   *
143   *
144   *
145   *
146   *
147   Defines SmallMatrix::EraseColumnPreservingOrder with two arguments: position
      and count of columns to delete (defualt 1)
148   BLOCK START - SmallMatrix::EraseColumnPreservingOrder
149   If there are no columns to delete, do nothing
150   Check that the start column is valid
151   Check that all columns are valid
152   Remove the columns
153   Get the data count to move
154   If there is data to move
155   Copy the data to the start of the removed position
156   And get all the data
157   End of check for data to move
158   BLOCK END - SmallMatrix::EraseColumnPreservingOrder
159   -
160   *
161   *
162   *
163   *
164   Defines SmallMatrix::EraseRow with one argument: row position
165   BLOCK START - SmallMatrix::EraseRow
166   If the row to delete is valid...
167   Loop through all elements in the row
168   Replace the row with...
169   The last row of data...
170   Repeat loop for all row elements
171   End check for valid row to delete
172   Resize the matrix with the new dimensions
173   BLOCK END - SmallMatrix::EraseRow
174   -
175   *
176   *
177   *
178   *
179   *
180   Defines SmallMatrix::EraseRowPreservingOrder with two arguments: a position
      and count to delete (default 1)
181   BLOCK START - SmallMatrix::EraseRowPreservingOrder
182   If all of the rows are valid...
183   Loop through all of the columns
184   Move data to the beginning of the erased section..
185   from beyond the end of the last erased row..
186   and include all data elements that still exist
187   Repeat move loop
188   End check for valid rows
189   Resize the matrix with the rows removed
190   BLOCK END - SmallMatrix::EraseRowPreservingOrder
191   -
192   *
193   *
194   *
195   *
196   Defines SmallMatrix::AppendRow with one argument: Rows to add
197   BLOCK START - SmallMatrix::Append Row
198   Resize array with the new row count
199   BLOCK END - SmallMatrix::Append Row
200   -
201   *
202   *
203   *
204   *
205   Defines SmallMatrix::AppendColumn with one argument: Rows to add
206   BLOCK START - SmallMatrix::AppendColumn
207   Resize array with the new row count
208   BLOCK END - SmallMatrix::AppendColumn
209   -
210   *
211   *
212   *
213   *
214   *
215   *
216   Defines SmallMatrix::Resize with two arguments: the new width and height
217   BLOCK START - SmallMatrix::Resize
218   Compute the new capacity
219   Declare a new pointer for the data
220   Declare a function pointer with a memcpy/move-like prototype
221   If the matrix needs to grow...
222   *
223   Allocates the proper size to the new data pointer
224   Assigns MemCpyT to the copy function pointer
225   Otherwise the matrix is large enough so...
226   *
227   Simply copy the data pointer
228   Assign MemMoveT to the copy function
229   End check for correct capacity
230   If the height isn't correct or the data pointers don't match..
231   If the current height is positive..
232   and the new height needs to be larger...
233   *
234   *
235   Loop across the matrix from the back
236   If we're looking at the new space, skip the loop step
237   Copy to the back of the new array with the adjusted height
238   From the old space
239   The amount that's smaller, the old height or the new height
240   Repeat loop until all data is copied
241   Otherwise the new matrix is smaller so...
242   *
243   Loop from the front...
244   If we're already past the new matrix, end the copy
245   Copy to the new matrix using the new height
246   From the old matrix, same offset
247   Using the smaller of the two matrices
248   Repeat loop for all data to copy
249   End check for growing/shrinking
250   End check for positive height
251   Match the array heights
252   If this is a new array...
253   Delete the old data pointer
254   Update to the new data pointer
255   Update the capacity 
256   End check for non-matching pointers
257   End check for non-matching height or data pointers
258   Match the new widths
259   BLOCK END - SmallMatrix::Resize
260   -
261   Defines SmallMatrix::Height with no arguments
262   BLOCK START - SmallMatrix::Height
263   Return the height of the matrix
264   BLOCK END - SmallMatrix::Height
265   -
266   Defines SmallMatrix::Width with no arguments
267   BLOCK START - SmallMatrix::Weight
268   Return the width of the matrix
269   BLOCK END - SmallMatrix::Weight
270   -
271   *
272   *
273   *
274   *
275   *
276   *
277   *
278   Defines SmallMatrix::Get with two arguments: the x and y position
279   BLOCK START - SmallMatrix::Get
280 
281 
282   BLOCK END - SmallMatrix::Get
283   -
284   *
285   *
286   *
287   *
288   *
289   *
290   *
291   Defines SmallMatrix::Get with two arguments: the x and y position
292   BLOCK START - SmallMatrix::Get
293   Confirm that the given coordinates are valid
294   Return the data at the coordinates (y-major)
295   BLOCK END - SmallMatrix::Get
296   -
297   *
298   *
299   *
300   *
301   *
302   *
303   Defines overloaded array access operator for SmallMatrix
304   BLOCK START - Overloading [] operator for SmallMatrix
305   Confirm that the x position is valid
306   Return the input column head
307   BLOCK END - Overloading [] operator for SmallMatrix
308   -
309   *
310   *
311   *
312   *
313   *
314   *
315   Defines overloaded array access operator for SmallMatrix
316   BLOCK START - Overloading [] operator for SmallMatrix
317   Confirm a valid column now
318   Return the input column head
319   BLOCK END - Overloading [] operator for SmallMatrix
320   BLOCK END - SmallMatrix
321   -
322   Header guard end