pcb:preferences_subsystem
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pcb:preferences_subsystem [2020/06/28 18:15] cparker |
pcb:preferences_subsystem [2020/06/28 19:23] cparker |
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| === 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 === | ||
pcb/preferences_subsystem.txt ยท Last modified: 2021/02/28 19:56 by cparker
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