From 0f11ac27b9b9dbdde216a700434b7fcdc47e1093 Mon Sep 17 00:00:00 2001
From: patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3>
Date: Sat, 10 Nov 2012 16:19:12 +0000
Subject: Still trying to recover directory contents

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5330 42af7a65-404d-4744-a932-0658087f49c3
---
 nuttx/libc/README.txt | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 nuttx/libc/README.txt

(limited to 'nuttx/libc/README.txt')

diff --git a/nuttx/libc/README.txt b/nuttx/libc/README.txt
new file mode 100644
index 000000000..e99304841
--- /dev/null
+++ b/nuttx/libc/README.txt
@@ -0,0 +1,85 @@
+lib
+===
+
+This directory contains numerous, small functions typically associated with
+what you would expect to find in a standard C library.  The sub-directories
+in this directory contain standard interface that can be executed by user-
+mode programs.
+
+Normally, NuttX is built with no protection and all threads running in kerne-
+mode.  In that model, there is no real architectural distinction between
+what is a kernel-mode program and what is a user-mode program; the system is
+more like on multi-threaded program that all runs in kernel-mode.
+
+But if the CONFIG_NUTTX_KERNEL option is selected, NuttX will be built into
+distinct user-mode and kernel-mode sections.  In that case, most of the
+code in the nuttx/ directory will run in kernel-mode with with exceptions
+of (1) the user-mode "proxies" found in syscall/proxies, and (2) the
+standard C library functions found in this directory.  In this build model,
+it is critical to separate the user-mode OS interfaces in this way.
+
+Sub-Directories
+===============
+
+The files in the lib/ directory are organized (mostly) according which file
+in the include/ directory provides the prototype for library functions.  So
+we have:
+
+  libgen    - libgen.h
+  fixedmath - fixedmath.h
+  math      - math.h
+  mqueue    - pthread.h
+  net       - Various network-related header files: netinet/ether.h, arpa/inet.h
+  pthread   - pthread.h
+  queue     - queue.h
+  sched     - sched.h
+  semaphore - semaphore.h
+  stdio     - stdio.h
+  stdlib    - stdlib.h
+  string    - string.h
+  time      - time.h
+  unistd    - unistd.h
+
+There is also a misc/ subdirectory that contains various internal functions
+and interfaces from header files that are too few to warrant their own sub-
+directory:
+
+ misc       - Nonstandard "glue" logic, debug.h, crc32.h, dirent.h
+
+Library Database
+================
+
+Information about functions available in the NuttX C library information is
+maintained in a database.  That "database" is implemented as a simple comma-
+separated-value file, lib.csv.  Most spreadsheets programs will accept this
+format and can be used to maintain the library database.
+
+This library database will (eventually) be used to generate symbol library
+symbol table information that can be exported to external applications.
+
+The format of the CSV file for each line is:
+
+  Field 1: Function name
+  Field 2: The header file that contains the function prototype
+  Field 3: Condition for compilation
+  Field 4: The type of function return value.
+  Field 5 - N+5: The type of each of the N formal parameters of the function
+
+Each type field has a format as follows:
+
+  type name:
+        For all simpler types
+  formal type | actual type: 
+        For array types where the form of the formal (eg. int parm[2])
+        differs from the type of actual passed parameter (eg. int*).  This
+        is necessary because you cannot do simple casts to array types.
+  formal type | union member actual type | union member fieldname:
+        A similar situation exists for unions.  For example, the formal
+        parameter type union sigval -- You cannot cast a uintptr_t to
+        a union sigval, but you can cast to the type of one of the union
+        member types when passing the actual paramter.  Similarly, we
+        cannot cast a union sigval to a uinptr_t either.  Rather, we need
+        to cast a specific union member fieldname to uintptr_t.
+
+NOTE: The tool mksymtab can be used to generate a symbol table from this CSV
+file.  See nuttx/tools/README.txt for further details about the use of mksymtab.
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