FoXy v0.8.0 is out

FoXy v0.8.0, a pure Fortran XML library with no C underneath, has been released, completing a rebuild that began at version 0.5 and was carried out with the help of an AI assistant. The release provides five types — xml_file for an in-memory DOM, xml_index for files too large to hold, xml_handler for streaming callbacks, xml_writer for element-by-element output, and xml_tag for single elements — and supports files of any size, including over 2 GiB. The library targets scientific code that reads case files as numbers and writes results metadata as it computes, returning typed errors such as XML_BAD_VALUE, XML_NOT_FOUND and XML_MALFORMED instead of requiring string parsing.

Fortran XML for poor people FoXy is a pure Fortran library to read, query, edit, and write XML, with no C underneath: use foxy and your code talks XML hopefully . It started as a small parser for another poor people project VTKFortran ; the last four releases 0.5 to 0.8 rebuilt it with the help of an AI assistant into what scientific code needs from XML at least in my mind, even though I prefer other kinds of I/O formats generally : case files read as numbers, results metadata written as you compute, and files of any size , including over 2 GiB. Five types, one for each way of working with a document: | Type | For | |---|---| | xml file | a whole document in memory a DOM : parse, query, edit, save | | xml index | a file too large to hold: tags and attributes, contents read on demand | | xml handler | a document of any size read once: your callbacks, nothing stored | | xml writer | a document of any size, written element by element to a file, a unit or memory | | xml tag | a single element: build it, parse it, write it | The common case: a solver reads its settings from XML. No string juggling, no read ..., : use foxy type xml file :: doc real R8P :: dt integer I4P :: steps call doc%parse filename='case.xml' call doc%get content id=doc%find path='case/time/dt' , value=dt call doc%get content id=doc%find path='case/time/steps' , value=steps values= into an allocatable array , with iostat / iomsg . A value that is not a number gives XML BAD VALUE and leaves your variable unchanged; a missing tag or attribute gives XML NOT FOUND . 1e3 is not accepted as an integer. parse returns XML MALFORMED with the first problem and its line: tag structure, names, duplicate attributes, a second root, text outside the root, malformed references, ill-formed UTF-8. ids = doc%select 'case/boundary @type="wall" ' attribute value ids = doc%select '// @unit ' any name, at any depth ids = doc%select '/case/boundary 2 ' the second boundary child ids = doc%select '//boundary @side~="^ east|west $" /velocity' regular expression / , // , , @a , @a="v" , @a~="re" , n among siblings. A malformed expression returns no IDs and the column of the problem in matching re, ... , using the StringiFor engine Python re syntax, linear time, no backtracking . find / find all : by prefix, by {uri}local , or with your own prefixes mapped to URIs. type xml writer :: w call w%open call w%start 'cell' call w%attribute 'dt', 0.1 R8P the shortest text that reads back: 0.1 call w%attribute 'extent', 0 I4P, 63 I4P, 0 I4P, 31 I4P call w%start 'volume' call w%text 1. R8P/3. R8P call w%end 'volume' call w%start 'center' call w%text 0.5 R8P, 0.25 R8P, 0. R8P , fmt=' F5.3 ' call w%end 'center' call w%close <cell dt="0.1" extent="0 63 0 31" <volume 0.3333333333333333</volume <center 0.500 0.250 0.000</center </cell 0.1 , not 1.000000000000000E-001 , or your own fmt= . A value too wide for the field is an error, not a row of asterisks. & < " ' , checks names, duplicate attributes, one root element, and PI targets. Errors are sticky and reported once, by close or set content / set attribute with value= / add tag parent=|before=|after= , set name , delete tag , then save . type, extends xml handler :: pressure sum ... contains procedure :: start element = on start procedure :: characters = on text procedure :: end element = on end endtype pressure sum call summer%parse filename='results.xml', iostat=iostat Extend xml handler , override the callbacks you need start and end tags, text, CDATA, comments, PIs, DOCTYPE, problems with their line , and the file is read in chunks with nothing stored; stop parsing ends it early. Your callbacks are plain type-bound procedures: I/O and side effects are allowed. For random access to files too large for a DOM, there is xml index : it scans the tags and attributes only, and reads content from the file when you ask for it stop at= stops the scan early . UTF-8, UTF-16, UTF-32 byte order mark or not , ISO-8859-1, Windows-1252, and US-ASCII sources are detected XML 1.0 Appendix F, then the declaration and converted to UTF-8 piece by piece. save writes UTF-8 and declares it. An encoding FoXy does not read is reported, not guessed. What I use it for, and what it is designed for: xml writer as the run goes, numbers formatted for you. VTKFortran writes its XML formats through FoXy. xml index or xml handler on files of hundreds of MB or over 2 GiB, without loading them. Performance: parsing is linear in the document size. A generated QuakeML-like catalogue of 100,000 tags 3 MB is parsed into the DOM in about 0.11 s and written back by stringify in 0.03 s gfortran 16, -O2 , a desktop CPU; fobis build --mode benchmark-gnu reproduces it . Known limits: entities declared in a DTD are not expanded, and there is no validation against a DTD or schema. 43 test programs, run with gfortran, nvfortran and ifx debug builds with runtime checks included . Chunked parsing is checked against whole-string parsing down to 1-character chunks, the streaming events against the DOM on every test file, and the index against the DOM tag by tag. Every sample in the documentation is a program compiled and run to produce the output shown, and CI fails if the output changes. The documentation has a tutorial https://fortran-foss-programmers.github.io/FoXy/manual/tutorial/01-first-document that builds the input and output of a small solver in nine chapters, a cookbook https://fortran-foss-programmers.github.io/FoXy/manual/cookbook , and an Upgrading https://fortran-foss-programmers.github.io/FoXy/guide/upgrading page listing the behaviour changes release by release. FoXy builds with FoBiS, fpm, or CMake, is tested with GNU gfortran, NVIDIA nvfortran, and Intel ifx, and is multi-licensed GPL v3, BSD 2-Clause, BSD 3-Clause, MIT, select the best fit for you . Feedback, issues, and contributions are welcome. Stefano