RNGT(5) File Formats Manual RNGT(5)

rngt — Rad-Net Gas Temperatures

rngt is a binary file format for storing gas temperatures. The temperatures are discretized according to the mesh of the gas. The mesh to which the temperatures are attached is described there but must be defined in a separate file, for example in an smsh(5) file. The number of temperatures and their order must therefore correspond to the data of the mesh to which they are attached, i.e. to the nodes or cells listed in the corresponding mesh.

A rngt file is actually a Star-Buffer file (see sbuf(5)). It starts with a header of 4 integers. The first integer is a power of two (usually 4096) that defines the size of the memory page in bytes (pagesize) on which the list of temperatures are aligned. By aligning data to pagesize, and depending on system requirements, memory mapping can be used to automatically load/unload pages on demand (see mmap(2)). The second integer is the size of the array, i.e. the number of temperatures stored in the list. The two remaining integers store the memory size (4 bytes) and the memory alignment (4 bytes) of a temperature.

Padding bytes follow the file header to align the listed temperatures to pagesize.

Padding bytes are finally added at the end of the file to align its overall size with the size of a page.

Data are encoded with respect to the little endian bytes ordering, i.e. least significant bytes are stored first.

The file format is as follows:

⟨rngt⟩ ::= ⟨pagesize⟩ ⟨size⟩ 4 4
⟨padding⟩
⟨temperatures⟩
⟨padding⟩
⟨pagesize⟩ ::= uint64_t
⟨size⟩ ::= uint64_t # Number of temperatures stored
⟨temperatures⟩ ::= float ... # In K
⟨padding⟩ ::= [int8_t ...]

mmap(2), sbuf(5), smsh(5)

The rngt format was first developed for the htrdr-planeto(1) program.

September 26, 2023 UNIX