NAME
Parse::GLSL - extract an Abstract Syntax Tree from GLSL text
VERSION
version 0.002
SYNOPSIS
use Parse::GLSL;
use Data::Dumper;
my $parser = Parse::GLSL->new;
my $txt = '';
while(my $line = <DATA>) {
if($line =~ /^\s*#\s*(?:(.*))$/) {
my $cmd = $1;
warn "Had directive [$cmd]\n";
} else {
$txt .= $line;
}
}
print Dumper $parser->from_string($txt);DESCRIPTION
Warning: This is a preview release, and the entire API is subject to change several times over the next few releases.
This module provides basic parsing for the OpenGL Shading Language (currently dealing with fragment and vertex shaders, eventually will be expanded to cover geometry, tesselation and compute shaders as well).
The GLSL document is parsed using Parser::MGC, rather than the reference 3D Labs GLSL parser implementation, and a Perl data structure is generated as output.
Currently very basic variable checking is performed - vars must be declared before use, so this would raise an error:
void main(void) {
vec2 tex_coord;
vec2 c = unknown_var * tex_coord.st;
}Further checks are planned in future versions.
The exact nature of the data structure returned is subject to change, so it's not currently documented.
METHODS
new
Constructor - see Parser::MGC for full details. This is defined here to override the standard string delimiter to " since C strings don't use the ' delimiter. Not that strings have much place in GLSL per se...
where_am_i
Reports current position in line if $self->{debug} is set to 2 or above.
parse
Parse the given GLSL string.
parse_item
Parse an "entry" in the GLSL text. Currently this consists of top-level variable declarations and function declarations.
parse_declaration
Parse a variable declaration.
parse_definition
Parse a "definition" (x = y), currently this also includes bare identifiers so that it works with "parse_declaration" but this behaviour is subject to change.
parse_type
Parse the variable type.
parse_parameter
Parse the parameters for a function definition.
parse_function
Parse a function definition and code block.
parse_block
Parse a block of statements (including the { ... } delimiters).
parse_statement
Parse a single statement. This includes the trailing ; since it's a terminator not a separator in GLSL.
parse_loopy_thing
Handle control statements like if, while, that sort of thing. Any comments about the name of this method should consider the first line in the "DESCRIPTION".
token_control_keyword
Parse a 'control keyword' (or 'loopy_thing' if you've been reading the other methods). That means if, while, and anything else that does(expression) { block }.
parse_expression
Parse an expression, such as fract(c) or 1 + 3 / 12 * vec3(1.0).
parse_nested_expression
Parse the bit inside an expression ... so not really a nested expression, more like an expression atom or component maybe?
token_operator
hey look it's a binary operator
token_function
Known built-in functions. Eventually these will be extracted to a separate definition block so that parameter types + counts can be verified.
token_preprocessor_directive
Parse a preprocessor directive.
Note that '#' is perfectly valid as a directive.
token_macro
Pick up on #defined (macro) values.
expand_macro
Attempt to expand the given macro.
token_glsl_ident
A GLSL identifier. Somewhat vague term, currently includes variables and qualified pieces (colour.r).
parse_statements
Parse more than one statement.
SEE ALSO
http://www.opengl.org - particularly the official "Orange Book"
OpenGL::Shader - if you want to use shaders with Perl
reference 3d Labs GLSL compiler
AUTHOR
Tom Molesworth <cpan@entitymodel.com>
LICENSE
Copyright Tom Molesworth 2011-2012. Licensed under the same terms as Perl itself.