89 lines
3.6 KiB
Plaintext
89 lines
3.6 KiB
Plaintext
lib
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===
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This directory contains numerous, small functions typically associated with
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what you would expect to find in a standard C library. The sub-directories
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in this directory contain standard interface that can be executed by user-
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mode programs.
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Normally, NuttX is built with no protection and all threads running in kerne-
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mode. In that model, there is no real architectural distinction between
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what is a kernel-mode program and what is a user-mode program; the system is
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more like on multi-threaded program that all runs in kernel-mode.
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But if the CONFIG_BUILD_PROTECTED option is selected, NuttX will be built
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into distinct user-mode and kernel-mode sections. In that case, most of the
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code in the nuttx/ directory will run in kernel-mode with with exceptions
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of (1) the user-mode "proxies" found in syscall/proxies, and (2) the
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standard C library functions found in this directory. In this build model,
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it is critical to separate the user-mode OS interfaces in this way.
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If CONFIG_BUILD_KERNEL is selected, then only a NuttX kernel will be built
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with no applications.
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Sub-Directories
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===============
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The files in the libc/ directory are organized (mostly) according which file
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in the include/ directory provides the prototype for library functions. So
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we have:
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audio - This part of the audio system: nuttx/audio/audio.h
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libgen - libgen.h
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fixedmath - fixedmath.h
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math - math.h
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net - Various network-related header files: netinet/ether.h, arpa/inet.h
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pthread - pthread.h
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queue - queue.h
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sched - sched.h
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semaphore - semaphore.h
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stdio - stdio.h
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stdlib - stdlib.h
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string - string.h
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time - time.h
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unistd - unistd.h
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There is also a misc/ subdirectory that contains various internal functions
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and interfaces from header files that are too few to warrant their own sub-
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directory:
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misc - Nonstandard "glue" logic, debug.h, crc32.h, dirent.h
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Library Database
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================
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Information about functions available in the NuttX C library information is
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maintained in a database. That "database" is implemented as a simple comma-
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separated-value file, libc.csv. Most spreadsheets programs will accept this
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format and can be used to maintain the library database.
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This library database will (eventually) be used to generate symbol library
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symbol table information that can be exported to external applications.
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The format of the CSV file for each line is:
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Field 1: Function name
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Field 2: The header file that contains the function prototype
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Field 3: Condition for compilation
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Field 4: The type of function return value.
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Field 5 - N+5: The type of each of the N formal parameters of the function
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Each type field has a format as follows:
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type name:
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For all simpler types
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formal type | actual type:
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For array types where the form of the formal (eg. int parm[2])
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differs from the type of actual passed parameter (eg. int*). This
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is necessary because you cannot do simple casts to array types.
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formal type | union member actual type | union member fieldname:
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A similar situation exists for unions. For example, the formal
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parameter type union sigval -- You cannot cast a uintptr_t to
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a union sigval, but you can cast to the type of one of the union
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member types when passing the actual parameter. Similarly, we
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cannot cast a union sigval to a uinptr_t either. Rather, we need
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to cast a specific union member fieldname to uintptr_t.
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NOTE: The tool mksymtab can be used to generate a symbol table from this CSV
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file. See nuttx/tools/README.txt for further details about the use of mksymtab.
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