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#!/usr/bin/perl
# \file
# cgissi.fcgi -- A FastCGI script to emulate Server-Side Includes
#
# At the time of writing, it supports #include, #fsize and #flastmod
#
use warnings;
use strict;
use Digest::MD5 qw(md5_base64);
use File::Spec;
use FCGI;
use POSIX qw(strftime);
# Content cache to avoid regenerating pages unless it's absolutely necessary
#
# This hash maps between the full local path to the URL data
# and a hash containing cache data. For example:
#
# { "/foo/bar/baz" =>
# { last_modified => 0123456789,
# data_digest => "base64(MD5($data))"
# data_last_modified => 0123456789,
# data => "generated page content",
# dependencies =>
# { "/foo/bar/bat" =>
# { last_modified => 0123456789,
# commands =>
# [
# { command => "include" | "fsize" | "flastmod",
# start_offset = 123,
# end_offset = 456
# },
# { command => "include" | "fsize" | "flastmod",
# start_offset = 678,
# end_offset = 901
# }
# ]
# }
# }
# }
# }
#
my %cache;
# Request object
my $request = FCGI::Request();
# Loop until the server tells us to quit
while ($request->Accept() >= 0) {
# Get document root for this request
my $docroot = $ENV{DOCUMENT_ROOT};
# Get path of item for this request
# Yes, this is hacky. It appears that REDIRECT_PATH contains
# the destination document resulting from content negotiation.
# As this is an absolute path, we strip the document root from it.
my ($path) = ($ENV{REDIRECT_PATH} =~ m/$docroot(.*)/);
# Find item in cache
my $cachedata = $cache{$docroot . $path};
# Determine if we need to (re)generate page
validate_cache_entry($docroot, $path, $cachedata);
# Refetch cache entry
# (as it may have been created by validate_cache_entry)
$cachedata = $cache{$docroot . $path};
# TODO It would be nice to send 304 responses where appropriate
# and also to pay attention to conditional requests namely
# If-(None-)Match and If-(Un)Modified-Since
# Cache-related headers
print "ETag: " . $$cachedata{data_digest} . "\r\n";
# Don't use %Z here, as perl's strftime appears to assume that the
# time is always in the local timezone
print "Last-Modified: " . strftime("%a, %d %b %Y %H:%M:%S GMT",
gmtime($$cachedata{data_last_modified})) . "\r\n";
# Send Content-Type header
print "Content-Type: text/html; charset=ISO-8859-1\r\n";
print "\r\n";
# And the page data
print $$cachedata{data};
}
################################################################################
# Run an include command
#
# \param filepath The full path of the file to include
# \param data Data buffer to append file data to (reference)
#
sub do_include
{
my ($filepath, $data) = @_;
if (-e $filepath) {
# Unlike Zeus, we don't recursively apply SSI.
open FILE, $filepath;
{
local $/ = undef;
$$data .= <FILE>;
}
close FILE;
}
}
# Run a fsize command
#
# \param filepath The full path of the file to measure the size of
# \param data Data buffer to append size to (reference)
#
sub do_fsize
{
my ($filepath, $data) = @_;
my @units = ( "B", "kB", "MB", "GB", "TB" ); # should be sufficient ;)
if (-e $filepath) {
my $size = -s $filepath;
my $index = 0;
while ($size > 1000) {
$size /= 1024;
$index++;
}
$$data .= sprintf("%.1f %s", $size, $units[$index]);
}
}
# Run a flastmod command
#
# \param filepath The full path of the file to get the modification time of
# \param data Data buffer to append modification time to (reference)
#
sub do_flastmod
{
my ($filepath, $data) = @_;
if (-e $filepath) {
my $mod_string =
strftime("%d %b %Y %R", gmtime((stat($filepath))[9]));
$$data .= $mod_string . " UTC";
}
}
# Process an include command
#
# \param command The command string to process
# \param data Data buffer to append output to (reference)
# \param docroot The document root
# \param path Path of the current document, relative to ::docroot
# \return The full path of the included file
#
sub process_include_command
{
my ($command, $data, $docroot, $path) = @_;
my $filepath;
if ($command =~ /file=/) {
my ($relpath) = ($command =~ m/file="(.*)"/);
my ($vol, $dirs, $file) =
File::Spec->splitpath($docroot . $path);
$filepath = File::Spec->rel2abs($relpath,
File::Spec->catpath($vol, $dirs, ""));
} elsif ($command =~ /virtual=/) {
my ($vpath) = ($command =~ m/virtual="(.*)"/);
if ($vpath =~ m#^/.*#) {
$filepath = $docroot . $vpath;
} else {
my ($vol, $dirs, $file) =
File::Spec->splitpath($docroot . $path);
$filepath = File::Spec->rel2abs($vpath,
File::Spec->catpath($vol, $dirs, ""));
}
}
do_include($filepath, $data);
return $filepath;
}
# Process an fsize command
#
# \param command The command string to process
# \param data Data buffer to append output to (reference)
# \param docroot The document root
# \param path Path of the current document, relative to ::docroot
# \return The full path of the included file
#
sub process_fsize_command
{
my ($command, $data, $docroot, $path) = @_;
my $filepath;
if ($command =~ /file=/) {
my ($relpath) = ($command =~ m/file="(.*)"/);
my ($vol, $dirs, $file) =
File::Spec->splitpath($docroot . $path);
$filepath = File::Spec->rel2abs($relpath,
File::Spec->catpath($vol, $dirs, ""));
} elsif ($command =~ /virtual=/) {
my ($vpath) = ($command =~ m/virtual="(.*)"/);
if ($vpath =~ m#^/.*#) {
$filepath = $docroot . $vpath;
} else {
my ($vol, $dirs, $file) =
File::Spec->splitpath($docroot . $path);
$filepath = File::Spec->rel2abs($vpath,
File::Spec->catpath($vol, $dirs, ""));
}
}
do_fsize($filepath, $data);
return $filepath;
}
# Process an flastmod command
#
# \param command The command string to process
# \param data Data buffer to append output to (reference)
# \param docroot The document root
# \param path Path of the current document, relative to ::docroot
# \return The full path of the included file
#
sub process_flastmod_command
{
my ($command, $data, $docroot, $path) = @_;
my $filepath;
if ($command =~ /file=/) {
my ($relpath) = ($command =~ m/file="(.*)"/);
my ($vol, $dirs, $file) =
File::Spec->splitpath($docroot . $path);
$filepath = File::Spec->rel2abs($relpath,
File::Spec->catpath($vol, $dirs, ""));
} elsif ($command =~ /virtual=/) {
my ($vpath) = ($command =~ m/virtual="(.*)"/);
if ($vpath =~ m#^/.*#) {
$filepath = $docroot . $vpath;
} else {
my ($vol, $dirs, $file) =
File::Spec->splitpath($docroot . $path);
$filepath = File::Spec->rel2abs($vpath,
File::Spec->catpath($vol, $dirs, ""));
}
}
do_flastmod($filepath, $data);
return $filepath;
}
# Complete parsing of and process a command string
#
# \param template Open file handle of template input
# \param char Current input character
# \param command The command string read so far
# \param data Buffer to append data into (reference)
# \param docroot The document root
# \param path Path of the current document relative to ::docroot
# \param start_offset Offset into template input of start of SSI command
# \param cacheentry The cache entry for the current document
#
sub process_command
{
my ($template, $char, $command, $data,
$docroot, $path, $start_offset, $cacheentry) = @_;
my $keyword = lc($command);
my $dash_count = 0;
my $filepath;
# See state machine documentation in generate_page_full for details of
# how this function works.
# Reject command if it's one we know nothing about
if ($keyword ne "include" && $keyword ne "fsize" &&
$keyword ne "flastmod") {
# ProcessCmd -> Initial transition occurs in generate_page_full
$$data .= "<!--#" . $command . $char;
return;
}
# Process the current input character
if ($char eq '-') {
# ProcessCmd -> ProcCmdDash
$dash_count++;
} else {
# ProcessCmd -> ProcessCmd
$command .= $char;
}
# Read rest of command string, then process command
while ($char = getc($template)) {
if ($char eq '-') {
# ProcessCmd -> ProcCmdDash / ProcCmdDash -> ProcCmdCT
$dash_count++;
} elsif ($dash_count == 2 && $char eq '>') {
# Run command (ProcCmdCT -> Initial transition occurs
# in generate_page_full)
if ($keyword eq "include") {
$filepath = process_include_command($command,
$data, $docroot, $path);
} elsif ($keyword eq "fsize") {
$filepath = process_fsize_command($command,
$data, $docroot, $path);
} elsif ($keyword eq "flastmod") {
$filepath = process_flastmod_command($command,
$data, $docroot, $path);
}
$$cacheentry{dependencies}{$filepath}{last_modified} =
(stat($filepath))[9];
push(@{$$cacheentry{dependencies}{$filepath}{commands}},
{ command => $keyword,
start_offset => $start_offset,
end_offset => tell($template)
});
return;
} else {
# ProcessCmd / ProcCmdDash / ProcCmdCT -> ProcessCmd
while ($dash_count > 0) {
$command .= "-";
$dash_count--;
}
$command .= $char;
}
}
}
# Fully generate a page.
# This involves parsing the page source looking for SSI commands.
#
# \param docroot The document root
# \param path Path of the current document relative to ::docroot
#
sub generate_page_full
{
my ($docroot, $path) = @_;
my $data = "";
my $in_tag = 0;
my $had_pling = 0;
my $dash_count = 0;
my $in_comment = 0;
my $had_hash = 0;
my $command = "";
my $start_offset = 0;
if (! -e $docroot . $path) {
# File doesn't exist
$cache{$docroot . $path}{data} = $data;
$cache{$docroot . $path}{data_digest} =
'"' . md5_base64($data) . '"';
$cache{$docroot . $path}{data_last_modified} = time;
return;
}
open my $template, $docroot . $path;
# Save document modification time into cache
my $lastmod = (stat($docroot . $path))[9];
$cache{$docroot . $path} = { last_modified => $lastmod };
my $cacheentry = $cache{$docroot . $path};
# Parse document template, looking for SSI comments
#
# This is basically a state machine, thus:
#
# State: Input: Next state: Output:
#
# Initial [^<] Initial Input character
# Initial '<' InTag None
#
# InTag [^!] Initial '<' followed by input
# InTag ! InTagPling None
#
# InTagPling [^-] Initial '<!' followed by input
# InTagPling '-' InTagPling1 None
#
# InTagPling1 [^-] Initial '<!-' followed by input
# InTagPling1 '-' InComment None
#
# InComment [^#] Initial '<!--' followed by input
# InComment '#' InCommentHash None
#
# InCommentHash [^a-zA-Z] ProcessCmd None
# InCommentHash [a-zA-Z] InCommentHash None [1]
#
# ProcessCmd n/a Initial '<!--#' followed by the
# command read in
# InCommentHash followed
# by input [2]
# ProcessCmd [^-] ProcessCmd None
# ProcessCmd '-' ProcCmdDash None
#
# ProcCmdDash [^-] ProcessCmd None [3]
# ProcCmdDash '-' ProcCmdCT None
#
# ProcCmdCT [^>] ProcessCmd None [4]
# ProcCmdCT '>' Initial Command specific [5]
#
# Notes:
#
# 1. This transition causes the input to be buffered as a command string
# 2. This transition only happens if the command read so far is not
# recognised
# 3. A dash is appended to the command string, however
# 4. A '>' is appended to the command string, however
# 5. The output is determined by running the command.
#
while (defined(my $char = getc($template))) {
if (!$in_comment && !$in_tag && $char eq '<') {
# Initial -> InTag
$start_offset = tell($template);
$in_tag = 1;
} elsif ($in_tag) {
if (!$had_pling) {
if ($char ne '!') {
# InTag -> Initial
$data .= "<" . $char;
$in_tag = 0;
} elsif ($char eq '!') {
# InTag -> InTagPling
$had_pling = 1;
}
} else {
if ($char ne '-') {
# InTagPling(1) -> Initial
$data .= "<!";
while ($dash_count > 0) {
$data .= "-";
$dash_count--;
}
$data .= $char;
$had_pling = 0;
$in_tag = 0;
} else {
# InTagPling -> InTagPling1
$dash_count++;
if ($dash_count == 2) {
# InTagPling1 -> InComment
$dash_count = 0;
$in_comment = 1;
$had_pling = 0;
$in_tag = 0;
}
}
}
} elsif ($in_comment) {
if (!$had_hash) {
if ($char ne '#') {
# InComment -> Initial
$data .= "<!--" . $char;
$in_comment = 0;
} else {
# InComment -> InCommentHash
$command = "";
$had_hash = 1;
}
} else {
my $c = lc($char);
if ('a' le $c && $c le 'z') {
# InCommentHash -> InCommentHash
$command .= $char;
} else {
# InCommentHash -> ProcessCmd
process_command($template, $char,
$command, \$data, $docroot,
$path, $start_offset,
$cacheentry);
# ProcessCmd/ProcCmdCT -> Initial
$had_hash = 0;
$in_comment = 0;
}
}
} else {
# Initial -> Initial
$data .= $char;
}
}
close $template;
# Save generated page data in cache
$$cacheentry{data} = $data;
$$cacheentry{data_digest} = '"' . md5_base64($data) . '"';
$$cacheentry{data_last_modified} = time;
}
# Partially generate a page.
# This involves using cached information to inject SSI data into a page
#
# \param docroot The document root
# \param path The path of the current document, relative to ::docroot
sub generate_page_partial
{
my ($docroot, $path) = @_;
if (! -e $docroot . $path) {
# File doesn't exist
$cache{$docroot . $path}{data} = "";
$cache{$docroot . $path}{data_digest} =
'"' . md5_base64("") . '"';
$cache{$docroot . $path}{data_last_modified} = time;
return;
}
# Get dependency hash
my $deps = $cache{$docroot . $path}{dependencies};
# Build command map for this page
my %cmds;
foreach my $dep (keys %{$deps}) {
my $index = 0;
foreach my $cmd (@{$$deps{$dep}{commands}}) {
# The key here is the index into the commands array
# prepended to the dependency URL. This ensures that
# we have unique map entries for each command.
$cmds{$index . $dep} = $cmd;
$index++;
}
}
# Sort command map by start_offset
my @sorted =
sort { # Unpack dependency URLs and command array indices
my ($a_index, $a_dep) = ($a =~ m/([0-9]+)(.*)/);
my ($b_index, $b_dep) = ($b =~ m/([0-9]+)(.*)/);
# Now compare the start offsets
$$deps{$a_dep}{commands}[$a_index]{start_offset} <=>
$$deps{$b_dep}{commands}[$b_index]{start_offset}
}
keys %cmds;
my $data = "";
my $temp;
my $curpos = 0;
my $template_length = 0;
# Open requested document
open TEMPLATE, $docroot . $path;
# Find its length
seek(TEMPLATE, 0, 2);
$template_length = tell(TEMPLATE);
seek(TEMPLATE, 0, 0);
# Iterate through commands, loading intervening chunks of template
foreach my $cmd (@sorted) {
# Unpack dependency URL and command array index
my ($index, $dep) = ($cmd =~ m/([0-9]+)(.*)/);
my $vars = $$deps{$dep};
my $length =
$$vars{commands}[$index]{start_offset} - $curpos - 1;
# Update last_modified time of this dependency (at least one
# must have changed for a partial regeneration to occur)
$$vars{last_modified} = (stat($dep))[9];
# Read template input from end of previous dependency
# to the start of this one
read(TEMPLATE, $temp, $length);
# Append it to our data buffer
$data .= $temp;
# Run this SSI command
if ($$vars{commands}[$index]{command} eq "include") {
do_include($dep, \$data);
} elsif ($$vars{commands}[$index]{command} eq "fsize") {
do_fsize($dep, \$data);
} elsif ($$vars{commands}[$index]{command} eq "flastmod") {
do_flastmod($dep, \$data);
}
# Skip over SSI command in template input
$curpos = $$vars{commands}[$index]{end_offset};
seek(TEMPLATE, $curpos, 0);
}
# Read any remaining template input
read(TEMPLATE, $temp, $template_length - $curpos);
$data .= $temp;
close TEMPLATE;
# Update document cache
$cache{$docroot . $path}{data} = $data;
$cache{$docroot . $path}{data_digest} = '"' . md5_base64($data) . '"';
$cache{$docroot . $path}{data_last_modified} = time;
}
# Validate a cache entry
#
# \param docroot The document root
# \param path The path of the current document, relative to ::docroot
# \param entry Current cache entry or undef if none
#
sub validate_cache_entry
{
my ($docroot, $path, $entry) = @_;
if (!$entry) {
# No entry -- generate one
generate_page_full($docroot, $path);
return;
}
if ((stat($docroot . $path))[9] > $$entry{last_modified}) {
# Page modified -- fully regenerate page
generate_page_full($docroot, $path);
return;
}
while (my ($dep, $data) = each(%{$entry->{dependencies}})) {
if ((stat($dep))[9] > $$data{last_modified}) {
# Dependency changed -- partially regenerate page
generate_page_partial($docroot, $path);
return;
}
}
# Otherwise, the cached data is valid
}
|