pcb:preferences_subsystem
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pcb:preferences_subsystem [2020/06/28 18:15] cparker |
pcb:preferences_subsystem [2020/07/26 13:58] cparker |
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| Line 81: | Line 81: | ||
| === Functions === | === Functions === | ||
| + | There are a number of key functions here: load_preferences, save_preferences, read_pref_file, write_pref_file, apply_preferences, collect_preferences, readers, and writers. Note that the file IO is being deliberately kept separate so that the actual file format is independent. Also, this allows data from a single file to be scanned more than once against different preference registries. We saw some pseudo-code for the load_preferences and save_preferences above (although it should have used apply_preferences and collect_preferences instead of spelling it out). So let's think about some of the others, again in pseudo-code (python...). | ||
| + | <code python> | ||
| + | def read_pref_file(filename): | ||
| + | with open(filename, r) as f: | ||
| + | f.seek(-1) # seek to the end | ||
| + | flen = f.tell() | ||
| + | r.rewind() | ||
| + | file_data = f.read(flen) | ||
| + | | ||
| + | # make sure to add a null at the end so file_data[flen] is a null char. | ||
| + | |||
| + | # find all the new lines | ||
| + | lines = [0] | ||
| + | for i in range(flen): | ||
| + | c = data[i] | ||
| + | if c == "\n": | ||
| + | data[i] = '\0' | ||
| + | if i + 1 < flen: # more data in file | ||
| + | lines.append(i+1) | ||
| + | | ||
| + | keys = [] | ||
| + | for l in lines: | ||
| + | # ignore lines that start with "#" | ||
| + | if data[l] == "#": continue | ||
| + | # ignore leading whitespace | ||
| + | i = l | ||
| + | while i < flen: | ||
| + | if data[l] in [" ", "\t"]: | ||
| + | i++ | ||
| + | | ||
| + | else: | ||
| + | keys.append[l] | ||
| + | break | ||
| + | | ||
| + | if len(keys) == 0: return | ||
| + | | ||
| + | values = [] | ||
| + | for k in keys: | ||
| + | i = k | ||
| + | while i =< flen: | ||
| + | c = data[i] | ||
| + | if (c == '\0') or (i == flen-1): | ||
| + | # no value for this key | ||
| + | # point it at the key? At a null? | ||
| + | values.append(i) | ||
| + | break | ||
| + | | ||
| + | elif c in [" ", "\t"]: | ||
| + | data[i] = '\0' | ||
| + | if i + 1 < flen: | ||
| + | values.append(i+1) | ||
| + | break | ||
| + | | ||
| + | i++ | ||
| + | | ||
| + | </code> | ||
| === File Format === | === File Format === | ||
| Line 117: | Line 173: | ||
| There will be a function for reading a preferences file, and a function for writing a preferences file. | There will be a function for reading a preferences file, and a function for writing a preferences file. | ||
| + | <code c> | ||
| void read_pref_file (char * fname) | void read_pref_file (char * fname) | ||
| { | { | ||
| Line 123: | Line 179: | ||
| /* open the file for reading */ | /* open the file for reading */ | ||
| } | } | ||
| + | </code> | ||
| + | <code c> | ||
| /* void pref_float (char * index_str, char * input_str, void *ptr) | /* void pref_float (char * index_str, char * input_str, void *ptr) | ||
| * This function takes an input string, converts it to a float, and assigns it to ptr. | * This function takes an input string, converts it to a float, and assigns it to ptr. | ||
| Line 139: | Line 196: | ||
| /* return 0; */ | /* return 0; */ | ||
| } | } | ||
| + | </code> | ||
| + | <code c> | ||
| /* char * float_pref(index_str, float fval) | /* char * float_pref(index_str, float fval) | ||
| * This function takes an input float and converts it to a string for storage in a preferences file. | * This function takes an input float and converts it to a string for storage in a preferences file. | ||
| Line 156: | Line 215: | ||
| return fstr; | return fstr; | ||
| } | } | ||
| + | </code> | ||
| Questions: | Questions: | ||
pcb/preferences_subsystem.txt ยท Last modified: 2021/02/28 19:56 by cparker
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