Annotation of libwww/Library/src/HTError.html, revision 2.17
2.1 frystyk 1: <HTML>
2: <HEAD>
3: <TITLE>Error message module for libwww</TITLE>
4: <NEXTID N="z1">
5: </HEAD>
6: <BODY>
2.9 frystyk 7: <H1>Reporting Errors and Messages to the Client</H1>
2.1 frystyk 8:
2.15 frystyk 9: This module maintaines a list of error messages that might occur
10: during load of a requested URL. The error list is put out to standard
11: output by a simple function that easily can be overwritten by a smart
12: server or client. The module is a part of the <A
13: HREF="Overview.html">CERN Common WWW Library</A>.<P>
14:
15: <NOTE><B>Note: </B></NOTE> At the moment, <A
16: HREF="HTErrorMsg.c">HTErrorMsg()</A> is called, if the flag
17: HTRequest->error_block is set to YES, then a stream has been put up
18: or taken down in the library and therefore it is <B>VERY</B> unsafe to
19: put anything more to the stream.
2.4 frystyk 20:
2.1 frystyk 21: <PRE>
22: #ifndef HTERROR_H
23: #define HTERROR_H
2.15 frystyk 24: #include "HTAccess.h"
2.1 frystyk 25: </PRE>
26:
2.3 frystyk 27: <H2>Data Structures</H2>
2.1 frystyk 28:
2.15 frystyk 29: The basic data structure is HTErrorInfo, but in addition the following
30: types are used:
2.1 frystyk 31:
2.3 frystyk 32: <H3>Error Numbers</H3>
2.1 frystyk 33:
2.15 frystyk 34: <NOTE><B>Note: </B></NOTE> All non-HTTP error codes have index numbers
35: > HTERR_HTTP_CODES, and they will not be shown in the error-message
36: generated.
37:
2.1 frystyk 38: <PRE>
39: typedef enum _HTErrorElement {
40: HTERR_OK = 0, /* 200 */
41: HTERR_CREATED, /* 201 */
42: HTERR_ACCEPTED, /* 202 */
43: HTERR_PARTIAL, /* 203 */
44: HTERR_NO_RESPONSE, /* 204 */
45: HTERR_MOVED, /* 301 */
46: HTERR_FOUND, /* 302 */
47: HTERR_METHOD, /* 303 */
48: HTERR_NOT_MODIFIED, /* 304 */
49: HTERR_BAD_REQUEST, /* 400 */
50: HTERR_UNAUTHORIZED, /* 401 */
51: HTERR_PAYMENT_REQUIRED, /* 402 */
52: HTERR_FORBIDDEN, /* 403 */
53: HTERR_NOT_FOUND, /* 404 */
54: HTERR_INTERNAL, /* 500 */
55: HTERR_NOT_IMPLEMENTED, /* 501 */
56: HTERR_HTTP_CODES_END, /* Put all non-HTTP status codes after this */
57: HTERR_NO_REMOTE_HOST,
2.13 frystyk 58: HTERR_NO_HOST,
2.1 frystyk 59: HTERR_FTP_SERVER,
60: HTERR_FTP_NO_RESPONSE,
61: HTERR_TIME_OUT,
2.2 frystyk 62: HTERR_GOPHER_SERVER,
63: HTERR_INTERRUPTED,
2.13 frystyk 64: HTERR_CON_INTR,
2.2 frystyk 65: HTERR_CSO_SERVER,
2.16 frystyk 66: HTERR_HTTP09, /* HTTP */
2.5 frystyk 67: HTERR_BAD_REPLY, /* HTTP */
2.16 frystyk 68: HTERR_UNKNOWN_AA,
2.5 frystyk 69: HTERR_NEWS_SERVER,
2.7 frystyk 70: HTERR_FILE_TO_FTP,
2.8 frystyk 71: HTERR_MAX_REDIRECT,
2.16 frystyk 72: HTERR_EOF,
2.14 frystyk 73: HTERR_WAIS_OVERFLOW,
74: HTERR_WAIS_MODULE,
2.12 frystyk 75: HTERR_WAIS_NO_CONNECT,
2.2 frystyk 76: HTERR_SYSTEM,
2.1 frystyk 77: HTERR_ELEMENTS /* This MUST be the last element */
78: } HTErrorElement;
2.3 frystyk 79:
80: typedef enum _HTErrSeverity {
81: ERR_FATAL = 0x1,
2.7 frystyk 82: ERR_NON_FATAL = 0x2,
83: ERR_WARNING = 0x4,
84: ERR_INFO = 0x8
2.3 frystyk 85: } HTErrSeverity;
86:
87: typedef struct _HTErrorInfo {
2.7 frystyk 88: int handle; /* Unique number in this stack */
2.3 frystyk 89: HTErrorElement element; /* Index number into HTErrorMsgInfo */
90: HTErrSeverity severity; /* A la VMS */
91: BOOL ignore; /* YES if msg should not go to user */
92: void * par; /* Explanation, e.g. filename */
93: unsigned int par_length; /* For copying by generic routine */
94: char * where; /* Which function */
95: } HTErrorInfo;
2.1 frystyk 96: </PRE>
97:
2.3 frystyk 98: <H2>Controling Globals</H2>
99:
2.15 frystyk 100: This variable dictates which errors should be put out when generating
101: the message to the user. The first four enumerations make it possible
102: to see `everything as bad or worse than' this level, e.g.
103: HT_ERR_SHOW_NON_FATAL shows messages of type HT_ERR_SHOW_NON_FATAL and
104: HT_ERR_SHOW_FATAL. <P>
105:
106: <B>Note:</B> The default value is made so that it only puts a message
107: to <EM>stderr</EM> if a `real' error has occurred. If a separate
108: widget is available for information and error messages then probably
109: HT_ERR_SHOW_DETAILED would be more appropriate.
2.3 frystyk 110:
111: <PRE>
112: typedef enum _HTErrorShow {
113: HT_ERR_SHOW_FATAL = 0x1,
114: HT_ERR_SHOW_NON_FATAL = 0x3,
115: HT_ERR_SHOW_WARNING = 0x7,
2.6 frystyk 116: HT_ERR_SHOW_INFO = 0xF,
117: HT_ERR_SHOW_PARS = 0x10,
118: HT_ERR_SHOW_LOCATION = 0x20,
119: HT_ERR_SHOW_IGNORE = 0x40,
120: HT_ERR_SHOW_FIRST = 0x80,
2.15 frystyk 121: HT_ERR_SHOW_LINKS = 0x100,
2.7 frystyk 122: HT_ERR_SHOW_DEFAULT = 0x13,
123: HT_ERR_SHOW_DETAILED = 0x1F,
2.10 frystyk 124: HT_ERR_SHOW_DEBUG = 0x7F
2.3 frystyk 125: } HTErrorShow;
126:
127: extern unsigned int HTErrorShowMask;
128: </PRE>
2.1 frystyk 129:
2.15 frystyk 130: This is the table containing the actual error-messages and links for
131: more information:
2.1 frystyk 132:
133: <PRE>
2.3 frystyk 134: typedef struct _HTErrorMsgInfo {
135: int code; /* Error number */
136: char * msg; /* Short explanation */
137: char * url; /* Explaning URL */
138: } HTErrorMsgInfo;
139:
140: extern HTErrorMsgInfo error_info[];
2.1 frystyk 141: </PRE>
142:
2.3 frystyk 143: <H2>Public Error Functions</H2>
144:
2.1 frystyk 145: <H3>Add an Error Message</H3>
146:
147: This function adds an error message to the error_stack list in the HTRequest
2.3 frystyk 148: structure. It always returns a negative value.
2.1 frystyk 149: <PRE>
2.3 frystyk 150: extern int HTErrorAdd PARAMS(( HTRequest * request,
2.1 frystyk 151: HTErrSeverity severity,
152: BOOL ignore,
153: int element,
154: void * par,
155: unsigned int par_length,
156: char * where));
2.2 frystyk 157: </PRE>
158:
159: <H3>Add a System Error Message</H3>
160:
2.15 frystyk 161: This function adds an error from a system call that initializes errno
162: or equivalent and adds it to the error_stack list in the HTRequest
163: structure. It always returns a negative value.
164:
2.2 frystyk 165: <PRE>
2.3 frystyk 166: extern int HTErrorSysAdd PARAMS(( HTRequest * request,
2.2 frystyk 167: HTErrSeverity severity,
168: BOOL ignore,
169: char * syscall));
2.1 frystyk 170: </PRE>
171:
172: <H3>Ignoring an Error Message</H3>
173:
2.15 frystyk 174: If an error message is not to be send to the user, e.g., output to the
175: stream, then the ignore flag must be turn on. Theese functions turns
176: it on for the latest error appended to the list or an arbitrary error
177: refered to by its handle.
178:
2.1 frystyk 179: <PRE>
2.7 frystyk 180: extern void HTErrorIgnore PARAMS((HTRequest * request, int handle));
181: extern void HTErrorIgnoreLast PARAMS((HTRequest * request));
2.1 frystyk 182: </PRE>
183:
2.15 frystyk 184: <H3>Handling Prefix for Links in Error Message</H3>
185:
186: Two functions handle the URL prefix of the links inside the error
187: message. They are quite obvious:
188:
189: <PRE>
2.17 ! frystyk 190: extern void HTErrorSetPrefix PARAMS((char *path));
! 191: extern CONST char *HTErrorGetPrefix NOPARAMS;
2.15 frystyk 192: </PRE>
193:
2.7 frystyk 194: <H3>Generating an Error Message (default to standard error)</H3>
2.3 frystyk 195:
2.8 frystyk 196: This function outputs the content of the error_stack to standard output
197: (used in Line Mode Browser), but smart clients and servers might overwrite
198: this function so that the error messages can be handled to the user in a nice
199: way. That is the reason for putting the actual implementation in HTErrorMsg.c,
200: that can be overwritten by clients and servers apart from Line Mode Browser.<P>
2.3 frystyk 201:
2.4 frystyk 202: <NOTE><B>Note: </B></NOTE>
2.1 frystyk 203:
2.8 frystyk 204: If a stream <EM>has</EM> been put up (and maybe taken down again) inside the
205: Library, then request->error_block has been set to YES. This indicates that
206: it is NOT possible any more to use the stream as output for the message.
2.1 frystyk 207: <PRE>
2.17 ! frystyk 208: extern void HTErrorMsg PARAMS((HTRequest * request));
2.1 frystyk 209: </PRE>
210:
211: <H3>Freeing an Error List</H3>
212:
2.8 frystyk 213: This is normally done when the HTRequest structure is freed but it might be
214: done at any other time in order to ignore a whole series of errors.
2.1 frystyk 215: <PRE>
2.17 ! frystyk 216: extern void HTErrorFree PARAMS((HTRequest * request));
2.1 frystyk 217: </PRE>
218:
219: <PRE>
220: #endif
221: </PRE>
222: end
223: </BODY>
224: </HTML>
225:
226:
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