1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 5. Samba Internals</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt02.html" title="Part II. Samba Basics"><link rel="prev" href="debug.html" title="Chapter 4. The samba DEBUG system"><link rel="next" href="CodingSuggestions.html" title="Chapter 6. Coding Suggestions"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 5. Samba Internals</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="debug.html">Prev</a> </td><th width="60%" align="center">Part II. Samba Basics</th><td width="20%" align="right"> <a accesskey="n" href="CodingSuggestions.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="internals"></a>Chapter 5. Samba Internals</h2></div><div><div class="author"><h3 class="author"><span class="firstname">David</span> <span class="surname">Chappell</span></h3><div class="affiliation"><div class="address"><p><code class="email"><<a href="mailto:David.Chappell@mail.trincoll.edu">David.Chappell@mail.trincoll.edu</a>></code></p></div></div></div></div><div><p class="pubdate">8 May 1996</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="internals.html#id2523545">Character Handling</a></span></dt><dt><span class="sect1"><a href="internals.html#id2523566">The new functions</a></span></dt><dt><span class="sect1"><a href="internals.html#id2523697">Macros in byteorder.h</a></span></dt><dd><dl><dt><span class="sect2"><a href="internals.html#id2523708">CVAL(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523719">PVAL(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523731">SCVAL(buf,pos,val)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523742">SVAL(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523755">IVAL(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523766">SVALS(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523778">IVALS(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523790">SSVAL(buf,pos,val)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523802">SIVAL(buf,pos,val)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523814">SSVALS(buf,pos,val)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523825">SIVALS(buf,pos,val)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523837">RSVAL(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523849">RIVAL(buf,pos)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523861">RSSVAL(buf,pos,val)</a></span></dt><dt><span class="sect2"><a href="internals.html#id2523873">RSIVAL(buf,pos,val)</a></span></dt></dl></dd><dt><span class="sect1"><a href="internals.html#id2523886">LAN Manager Samba API</a></span></dt><dd><dl><dt><span class="sect2"><a href="internals.html#id2523915">Parameters</a></span></dt><dt><span class="sect2"><a href="internals.html#id2524040">Return value</a></span></dt></dl></dd><dt><span class="sect1"><a href="internals.html#id2524112">Code character table</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523545"></a>Character Handling</h2></div></div></div><p>
2 This section describes character set handling in Samba, as implemented in
5 In the past Samba had very ad-hoc character set handling. Scattered
6 throughout the code were numerous calls which converted particular
7 strings to/from DOS codepages. The problem is that there was no way of
8 telling if a particular char* is in dos codepage or unix
9 codepage. This led to a nightmare of code that tried to cope with
10 particular cases without handlingt the general case.
11 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523566"></a>The new functions</h2></div></div></div><p>
12 The new system works like this:
13 </p><div class="orderedlist"><ol type="1"><li><p>
14 all char* strings inside Samba are "unix" strings. These are
15 multi-byte strings that are in the charset defined by the "unix
16 charset" option in smb.conf.
18 there is no single fixed character set for unix strings, but any
19 character set that is used does need the following properties:
20 </p><div class="orderedlist"><ol type="a"><li><p>
21 must not contain NULLs except for termination
23 must be 7-bit compatible with C strings, so that a constant
24 string or character in C will be byte-for-byte identical to the
25 equivalent string in the chosen character set.
27 when you uppercase or lowercase a string it does not become
28 longer than the original string
30 must be able to correctly hold all characters that your client
32 </p></li></ol></div><p>
33 For example, UTF-8 is fine, and most multi-byte asian character sets
34 are fine, but UCS2 could not be used for unix strings as they
37 when you need to put a string into a buffer that will be sent on the
38 wire, or you need a string in a character set format that is
39 compatible with the clients character set then you need to use a
40 pull_ or push_ function. The pull_ functions pull a string from a
41 wire buffer into a (multi-byte) unix string. The push_ functions
42 push a string out to a wire buffer.
44 the two main pull_ and push_ functions you need to understand are
45 pull_string and push_string. These functions take a base pointer
46 that should point at the start of the SMB packet that the string is
47 in. The functions will check the flags field in this packet to
48 automatically determine if the packet is marked as a unicode packet,
49 and they will choose whether to use unicode for this string based on
50 that flag. You may also force this decision using the STR_UNICODE or
51 STR_ASCII flags. For use in smbd/ and libsmb/ there are wrapper
52 functions clistr_ and srvstr_ that call the pull_/push_ functions
53 with the appropriate first argument.
55 You may also call the pull_ascii/pull_ucs2 or push_ascii/push_ucs2
56 functions if you know that a particular string is ascii or
57 unicode. There are also a number of other convenience functions in
58 charcnv.c that call the pull_/push_ functions with particularly
59 common arguments, such as pull_ascii_pstring()
61 The biggest thing to remember is that internal (unix) strings in Samba
62 may now contain multi-byte characters. This means you cannot assume
63 that characters are always 1 byte long. Often this means that you will
64 have to convert strings to ucs2 and back again in order to do some
65 (seemingly) simple task. For examples of how to do this see functions
66 like strchr_m(). I know this is very slow, and we will eventually
67 speed it up but right now we want this stuff correct not fast.
69 all lp_ functions now return unix strings. The magic "DOS" flag on
72 all vfs functions take unix strings. Don't convert when passing to them
73 </p></li></ol></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523697"></a>Macros in byteorder.h</h2></div></div></div><p>
74 This section describes the macros defined in byteorder.h. These macros
75 are used extensively in the Samba code.
76 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523708"></a>CVAL(buf,pos)</h3></div></div></div><p>
77 returns the byte at offset pos within buffer buf as an unsigned character.
78 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523719"></a>PVAL(buf,pos)</h3></div></div></div><p>returns the value of CVAL(buf,pos) cast to type unsigned integer.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523731"></a>SCVAL(buf,pos,val)</h3></div></div></div><p>sets the byte at offset pos within buffer buf to value val.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523742"></a>SVAL(buf,pos)</h3></div></div></div><p>
79 returns the value of the unsigned short (16 bit) little-endian integer at
80 offset pos within buffer buf. An integer of this type is sometimes
81 refered to as "USHORT".
82 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523755"></a>IVAL(buf,pos)</h3></div></div></div><p>returns the value of the unsigned 32 bit little-endian integer at offset
83 pos within buffer buf.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523766"></a>SVALS(buf,pos)</h3></div></div></div><p>returns the value of the signed short (16 bit) little-endian integer at
84 offset pos within buffer buf.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523778"></a>IVALS(buf,pos)</h3></div></div></div><p>returns the value of the signed 32 bit little-endian integer at offset pos
85 within buffer buf.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523790"></a>SSVAL(buf,pos,val)</h3></div></div></div><p>sets the unsigned short (16 bit) little-endian integer at offset pos within
86 buffer buf to value val.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523802"></a>SIVAL(buf,pos,val)</h3></div></div></div><p>sets the unsigned 32 bit little-endian integer at offset pos within buffer
87 buf to the value val.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523814"></a>SSVALS(buf,pos,val)</h3></div></div></div><p>sets the short (16 bit) signed little-endian integer at offset pos within
88 buffer buf to the value val.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523825"></a>SIVALS(buf,pos,val)</h3></div></div></div><p>sets the signed 32 bit little-endian integer at offset pos withing buffer
89 buf to the value val.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523837"></a>RSVAL(buf,pos)</h3></div></div></div><p>returns the value of the unsigned short (16 bit) big-endian integer at
90 offset pos within buffer buf.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523849"></a>RIVAL(buf,pos)</h3></div></div></div><p>returns the value of the unsigned 32 bit big-endian integer at offset
91 pos within buffer buf.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523861"></a>RSSVAL(buf,pos,val)</h3></div></div></div><p>sets the value of the unsigned short (16 bit) big-endian integer at
92 offset pos within buffer buf to value val.
93 refered to as "USHORT".</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523873"></a>RSIVAL(buf,pos,val)</h3></div></div></div><p>sets the value of the unsigned 32 bit big-endian integer at offset
94 pos within buffer buf to value val.</p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523886"></a>LAN Manager Samba API</h2></div></div></div><p>
95 This section describes the functions need to make a LAN Manager RPC call.
96 This information had been obtained by examining the Samba code and the LAN
97 Manager 2.0 API documentation. It should not be considered entirely
100 </p><pre class="programlisting">
101 call_api(int prcnt, int drcnt, int mprcnt, int mdrcnt,
102 char *param, char *data, char **rparam, char **rdata);
105 This function is defined in client.c. It uses an SMB transaction to call a
107 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523915"></a>Parameters</h3></div></div></div><p>The parameters are as follows:</p><div class="orderedlist"><ol type="1"><li><p>
108 prcnt: the number of bytes of parameters begin sent.
110 drcnt: the number of bytes of data begin sent.
112 mprcnt: the maximum number of bytes of parameters which should be returned
114 mdrcnt: the maximum number of bytes of data which should be returned
116 param: a pointer to the parameters to be sent.
118 data: a pointer to the data to be sent.
120 rparam: a pointer to a pointer which will be set to point to the returned
121 paramters. The caller of call_api() must deallocate this memory.
123 rdata: a pointer to a pointer which will be set to point to the returned
124 data. The caller of call_api() must deallocate this memory.
125 </p></li></ol></div><p>
126 These are the parameters which you ought to send, in the order of their
127 appearance in the parameter block:
128 </p><div class="orderedlist"><ol type="1"><li><p>
129 An unsigned 16 bit integer API number. You should set this value with
130 SSVAL(). I do not know where these numbers are described.
132 An ASCIIZ string describing the parameters to the API function as defined
133 in the LAN Manager documentation. The first parameter, which is the server
134 name, is ommited. This string is based uppon the API function as described
135 in the manual, not the data which is actually passed.
137 An ASCIIZ string describing the data structure which ought to be returned.
139 Any parameters which appear in the function call, as defined in the LAN
140 Manager API documentation, after the "Server" and up to and including the
143 An unsigned 16 bit integer which gives the size in bytes of the buffer we
144 will use to receive the returned array of data structures. Presumably this
145 should be the same as mdrcnt. This value should be set with SSVAL().
147 An ASCIIZ string describing substructures which should be returned. If no
148 substructures apply, this string is of zero length.
149 </p></li></ol></div><p>
150 The code in client.c always calls call_api() with no data. It is unclear
151 when a non-zero length data buffer would be sent.
152 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2524040"></a>Return value</h3></div></div></div><p>
153 The returned parameters (pointed to by rparam), in their order of appearance
154 are:</p><div class="orderedlist"><ol type="1"><li><p>
155 An unsigned 16 bit integer which contains the API function's return code.
156 This value should be read with SVAL().
158 An adjustment which tells the amount by which pointers in the returned
159 data should be adjusted. This value should be read with SVAL(). Basically,
160 the address of the start of the returned data buffer should have the returned
161 pointer value added to it and then have this value subtracted from it in
162 order to obtain the currect offset into the returned data buffer.
164 A count of the number of elements in the array of structures returned.
165 It is also possible that this may sometimes be the number of bytes returned.
166 </p></li></ol></div><p>
167 When call_api() returns, rparam points to the returned parameters. The
168 first if these is the result code. It will be zero if the API call
169 suceeded. This value by be read with "SVAL(rparam,0)".
171 The second parameter may be read as "SVAL(rparam,2)". It is a 16 bit offset
172 which indicates what the base address of the returned data buffer was when
173 it was built on the server. It should be used to correct pointer before
176 The returned data buffer contains the array of returned data structures.
177 Note that all pointers must be adjusted before use. The function
178 fix_char_ptr() in client.c can be used for this purpose.
180 The third parameter (which may be read as "SVAL(rparam,4)") has something to
181 do with indicating the amount of data returned or possibly the amount of
182 data which can be returned if enough buffer space is allowed.
183 </p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2524112"></a>Code character table</h2></div></div></div><p>
184 Certain data structures are described by means of ASCIIz strings containing
185 code characters. These are the code characters:
186 </p><div class="orderedlist"><ol type="1"><li><p>
187 W a type byte little-endian unsigned integer
189 N a count of substructures which follow
191 D a four byte little-endian unsigned integer
193 B a byte (with optional count expressed as trailing ASCII digits)
195 z a four byte offset to a NULL terminated string
197 l a four byte offset to non-string user data
199 b an offset to data (with count expressed as trailing ASCII digits)
201 r pointer to returned data buffer???
203 L length in bytes of returned data buffer???
205 h number of bytes of information available???
206 </p></li></ol></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="debug.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="CodingSuggestions.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 4. The samba DEBUG system </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 6. Coding Suggestions</td></tr></table></div></body></html>
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