fortran-yyjson

Modern Fortran bindings for yyjson, a fast, portable, ANSI C JSON library.

Requirements

• A Fortran compiler supporting the Fortran 2008 standard or later (gfortran, ifx, nvfortran, flang, ...).
• A C compiler (yyjson itself, and the glue layer, are plain C).
• fpm or CMake (>= 3.16) to build and test the package.

This package is not published to the official fpm registry (it has been unmaintained for a while) — depend on it directly via git instead.

Installation

fpm

Add this package as a git dependency in your fpm.toml:

[dependencies]
fortran-yyjson = { git = "https://github.com/AnmiTaliDev/fortran-yyjson.git" }

CMake

Alternatively, clone the repository and build/install it with CMake:

git clone https://github.com/AnmiTaliDev/fortran-yyjson.git
cmake -S fortran-yyjson -B build -DCMAKE_INSTALL_PREFIX=/usr/local
cmake --build build
cmake --install build

This installs the static library, the compiled .mod files, and a fortran-yyjson.pc pkg-config file, so downstream projects can pick up the compiler and linker flags with:

gfortran my_program.f90 -o my_program $(pkg-config --cflags --libs fortran-yyjson)

You can also add it as a subdirectory or via FetchContent/find_package in another CMake project and link against the fortran-yyjson::fortran-yyjson target.

Building

With fpm:

fpm build
fpm test
fpm run --example read_json
fpm run --example write_json
fpm run --example mutate_json

With CMake:

cmake -S . -B build
cmake --build build
ctest --test-dir build

Examples and tests are built by default when CMake is configured directly on this repository. Pass -DBUILD_TESTING=OFF and/or -DBUILD_EXAMPLES=OFF to skip them (they are already off by default when this project is pulled in as a CMake subdirectory of another project).

Usage

Reading JSON

use yyjson_module

type(json_document) :: doc
type(json_value) :: root, name_val

doc = json_parse('{"name":"Mash","star":4,"hits":[2,2,1,3]}')
if (.not. doc%is_valid()) stop "invalid JSON"

root = doc%root()
name_val = root%object_get("name")
print *, name_val%to_chars()

call doc%destroy()

Iterating arrays and objects

type(json_array_iterator) :: it
type(json_value) :: item

it = root%object_get("hits")%array_iterator()
do while (it%has_next())
  item = it%next()
  print *, item%to_integer()
end do

Writing JSON

use yyjson_module

type(json_mut_document) :: doc
type(json_mut_value) :: root
character(len=:), allocatable :: text

call doc%init()
root = doc%new_object()
call doc%object_add_string(root, "name", "Mash")
call doc%object_add_integer(root, "star", 4_c_int64_t)
call doc%set_root(root)

text = doc%to_chars(pretty=.true.)
print *, text

call doc%destroy()

See example/read_json.f90, example/write_json.f90, and example/mutate_json.f90 for complete, runnable programs.

API overview

Type	Purpose
json_document	Owns a parsed, immutable JSON value tree.
json_value	A handle to a single immutable JSON value.
json_mut_document	Owns a document being built or edited.
json_mut_value	A handle to a single mutable JSON value.
json_array_iterator	Forward iterator over an immutable JSON array.
json_object_iterator	Forward iterator over an immutable JSON object.

Documents own the memory of every value inside them; values themselves are lightweight, non-owning handles that stay valid as long as their document is not destroyed.

License

This project is released under the MIT License. It bundles yyjson, which is also MIT licensed. See LICENSE for full text and copyright notices.

Author

AnmiTaliDev anmitalidev@nuros.org