diff options
Diffstat (limited to 'Utility/HtmlDetect.hs')
| -rw-r--r-- | Utility/HtmlDetect.hs | 25 |
1 files changed, 18 insertions, 7 deletions
diff --git a/Utility/HtmlDetect.hs b/Utility/HtmlDetect.hs index 57a56c95f..bf0839e9e 100644 --- a/Utility/HtmlDetect.hs +++ b/Utility/HtmlDetect.hs @@ -9,20 +9,20 @@ module Utility.HtmlDetect where import Text.HTML.TagSoup import Data.Char +import qualified Data.ByteString.Lazy as B +import qualified Data.ByteString.Lazy.Char8 as B8 --- | Detect if a string is a html document. +-- | Detect if a String is a html document. -- --- The document many not be valid, and will still be detected as html, --- as long as it starts with a "<html>" or "<!DOCTYPE html>" tag. +-- The document many not be valid, or may be truncated, and will +-- still be detected as html, as long as it starts with a +-- "<html>" or "<!DOCTYPE html>" tag. -- -- Html fragments like "<p>this</p>" are not detected as being html, -- although some browsers may chose to render them as html. isHtml :: String -> Bool -isHtml = evaluate . canonicalizeTags . parseTags . shorten +isHtml = evaluate . canonicalizeTags . parseTags . take htmlPrefixLength where - -- We only care about the beginning of the file, - -- so although tagsoup parses lazily anyway, truncate it. - shorten = take 16384 evaluate (TagOpen "!DOCTYPE" ((t, _):_):_) = map toLower t == "html" evaluate (TagOpen "html" _:_) = True -- Allow some leading whitespace before the tag. @@ -33,3 +33,14 @@ isHtml = evaluate . canonicalizeTags . parseTags . shorten -- tag, but easy to allow for. evaluate (TagComment _:rest) = evaluate rest evaluate _ = False + +-- | Detect if a ByteString is a html document. +isHtmlBs :: B.ByteString -> Bool +-- The encoding of the ByteString is not known, but isHtml only +-- looks for ascii strings. +isHtmlBs = isHtml . B8.unpack + +-- | How much of the beginning of a html document is needed to detect it. +-- (conservatively) +htmlPrefixLength :: Int +htmlPrefixLength = 8192 |