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diff --git a/usr.bin/vi/docs/internals/structures b/usr.bin/vi/docs/internals/structures new file mode 100644 index 000000000000..d49ab65cbeed --- /dev/null +++ b/usr.bin/vi/docs/internals/structures @@ -0,0 +1,61 @@ +# @(#)structures 5.2 (Berkeley) 11/1/93 + +There are three major data structures in this package. The first is a +single global structure (named GS) which contains information common to +all files and screens. It's really pretty tiny, and functions more as a +single place to hang things than anything else. + +The second and third structures are the file structures (named EXF) and +the screen structures (named SCR). They contain information theoretically +unique to a screen or file, respectively. Each SCR structure has a set +of functions which update the screen and/or return information about the +screen from the underlying screen package. + +The GS structure contains linked lists SCR structures. The structures +can also be classed by persistence. The GS structure never goes away +and the SCR structure persists over instances of files. + +File names have different properties than files themselves, so the name +information for a file is held in an FREF structure which is chained from +the SCR structure. + +In general, functions are always passed an SCR structure and often an EXF +structure as well. The SCR structure is necessary for any routine that +wishes to talk to the screen, the EXF structure is necessary for any +routine that wants to modify the file. The relationship between an SCR +structure and its underlying EXF structure is not fixed, and although you +can translate from an SCR to the underlying EXF, it is discouraged. If +this becomes too onerous, I suspect I'll just stop passing around the EXF +in the future. + +The naming of the structures is consistent across the program. (Macros +even depend on it, so don't try and change it!) The global structure is +"gp", the screen structure is "sp", and the file structure is "ep". + +A few other data structures: + +TEXT In nvi/cut.h. This structure describes a portion of a line, + and is used by the input routines and as the "line" part of a + cut buffer. + +CB In nvi/cut.h. A cut buffer. A cut buffer is a place to + hang a list of TEXT structures. + +MARK In nvi/mark.h. A cursor position, consisting of a line number + and a column number. + +MSG In nvi/msg.h. A chain of messages for the user. + +SEQ In nvi/seq.h. An abbreviation or a map entry. + +EXCMDARG + In nvi/ex/excmd.h.stub. The structure that gets passed around + to the functions that implement the ex commands. (The main + ex command loop (see nvi/ex/ex.c) builds this up and then passes + it to the ex functions.) + +VICMDARG + In nvi/vi/vcmd.h. The structure that gets passed around to the + functions that implement the vi commands. (The main vi command + loop (see nvi/vi/vi.c) builds this up and then passes it to the + vi functions.) |