Description
This code generator produces the PIC assembler code to look for keywords
in a string or a serial ASCII stream.
Parsing routine receives one character at a time and returns the keyword
code, or the next state, or error code. The keywords codes are given in the
order they were written, starting from 1.
You can specify whether keywords are matched as the whole words or just starting
unique part. This let's you use shorthand names for the keywords. Also, case
insensitiveness can be specified.
The routine can skip whitespaces before a keyword. Enter the desired characters
in the form entry Whitespaces. In some cases it's probably better to delete
carriage return (0x0d) or line feed (0x0a) characters if you don't need them,
or add some others. To detect the end of a keyword the routine needs to know
what characters separate keywords in the text stream (form entry Delimiters).
Often, they are the same as whitespaces, but you might want to add '\0' to
work with zero terminated strings, or '(' in case the keyword is a function
name, e.g. Speed(100). A delimiter character is received as a look-ahead
character after a keyword matched to make sure that the keyword ended.
The routine is implemented as a variation of state machine, without explicit
tables. The routine is a relatively fast runner, since it compares a character
to a minimum number of constant characters, just enough to disambiguate the
text meaning.
The size of the generated code is directly related to the number of keywords
and their length. It takes about four instructions of program memory per
each character in the text area plus jump table and a couple of small routines.
See example on how to call the parsing
routine. |
