/**************************************************************************** * libs/libc/misc/lib_slcddecode.c * Decoding side of the SLCD CODEC * * Copyright (C) 2013 Gregory Nutt. All rights reserved. * Authors: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /* Indices, counts, helper macros ******************************************/ #define NDX_ESC 0 #define NDX_BRACKET 1 #define NDX_CODE3 2 #define NDX_COUNTH 2 #define NDX_COUNTL 3 #define NDX_CODE5 4 #define NCH_ESC 1 #define NCH_BRACKET 2 #define NCH_CODE3 3 #define NCH_COUNTH 3 #define NCH_COUNTL 4 #define NCH_CODE5 5 #define IS_HEX(a) ((((a) >= '0') && ((a) <= '9')) || \ (((a) >= 'a') && ((a) <= 'f'))) #define CODE_MIN ('A' + FIRST_SLCDCODE) #define CODE_MAX ('A' + LAST_SLCDCODE) #define IS_CODE(a) (((a) >= CODE_MIN) && ((a) <= CODE_MAX)) #define CODE_RETURN(a) (enum slcdcode_e)((a) - 'A') /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: slcd_nibble * * Description: * Convert a ASCII hexadecimal character (using only lower case alphabetics * into a binary nibble * * Input Parameters: * ascii - The nibble characgter. * * Returned Value: * The binary value of the nibble. * ****************************************************************************/ static uint8_t slcd_nibble(uint8_t ascii) { if (ascii >= '0' && ascii <= '9') { return ascii - '0'; } else { return ascii - 'a'; } } /**************************************************************************** * Name: slcd_reget * * Description: * We have unused characters from the last, unsuccessful decode attempt. * Return one of these instead of the new character from the stream. * * Input Parameters: * stream - An instance of lib_instream_s to do the low-level get * operation. * pch - The location character to save the returned value. This may be * either a normal, character code or a special command from enum * slcd_keycode_e * * Returned Value: * Always SLCDRET_CHAR * ****************************************************************************/ static enum slcdret_e slcd_reget(FAR struct slcdstate_s *state, FAR uint8_t *pch, FAR uint8_t *parg) { /* Return the next character */ *pch = state->buf[state->ndx]; *parg = 0; /* Bump up the indices and return false (meaning a normal character) */ state->ndx++; state->nch--; return SLCDRET_CHAR; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: slcd_decode * * Description: * Get one byte of data or special command from the application provided * input buffer. * * Input Parameters: * stream - An instance of lib_instream_s to do the low-level get * operation. * state - A user provided buffer to support parsing. This structure * should be cleared the first time that slcd_decode is called. * pch - The location to save the returned value. This may be * either a normal, character code or a special command from enum * slcdcode_e, depending on the return value from slcd_decode() * parg - The location to save the count argument that accompanies some * special actions * * Returned Value: * * false: Normal character * true: Special SLCD action code with possible argument * ****************************************************************************/ enum slcdret_e slcd_decode(FAR struct lib_instream_s *stream, FAR struct slcdstate_s *state, FAR uint8_t *pch, FAR uint8_t *parg) { enum slcdcode_e code; uint8_t count; int ch; DEBUGASSERT(stream && state && pch && parg); /* Are their ungotten characters from the last, failed parse? */ if (state->nch > 0) { /* Yes, return the next ungotten character */ return slcd_reget(state, pch, parg); } state->ndx = 0; /* No, ungotten characters. Get the next character from the buffer. */ ch = stream->get(stream); if (ch == EOF) { /* End of file/stream (or perhaps an I/O error) */ return SLCDRET_EOF; } /* Save the character (whatever it is) in case we fail parsing later */ state->buf[NDX_ESC] = (uint8_t)ch; state->nch = NCH_ESC; /* Check for the beginning of an escape sequence */ if (ch != ASCII_ESC) { /* Not the beginning of an escape sequence. Return the character. */ return slcd_reget(state, pch, parg); } /* Get the next character from the buffer */ ch = stream->get(stream); if (ch == EOF) { /* End of file/stream. Return the escape character now. We will * return the EOF indication next time. */ return slcd_reget(state, pch, parg); } /* Save the character (whatever it is) in case we fail parsing later */ state->buf[NDX_BRACKET] = ch; state->nch = NCH_BRACKET; /* Check for ESC-[ */ if (ch != '[') { /* Not the beginning of an escape sequence. Return the ESC now, * return the following characters later. */ lcderr("ERROR: Parsing failed: ESC followed by %02x\n", ch); return slcd_reget(state, pch, parg); } /* Get the next character from the buffer */ ch = stream->get(stream); if (ch == EOF) { /* End of file/stream. Return the ESC now; return the following * characters later. */ return slcd_reget(state, pch, parg); } /* If the next character is a hexidecimal value (with lower case * alphabetic characters), then we are parsing a 5-byte sequence. */ if (!IS_HEX(ch)) { /* Decode the value following the bracket */ code = CODE_RETURN(ch); count = 0; /* Verify the special CLCD action code */ if (code < (int)FIRST_SLCDCODE || code > (int)LAST_SLCDCODE) { lcderr("ERROR: Parsing failed: ESC-L followed by %02x\n", ch); /* Not a special command code.. put the character in the reget * buffer. */ state->buf[NDX_CODE3] = (uint8_t)ch; state->nch = NCH_CODE3; /* Return the ESC now and the next two characters later. */ return slcd_reget(state, pch, parg); } } else { /* Save the first character of the two byte hexidecimal number */ state->buf[NDX_COUNTH] = (uint8_t)ch; state->nch = NCH_COUNTH; /* Get the next character from the buffer */ ch = stream->get(stream); if (ch == EOF) { /* End of file/stream. Return the ESC now; return the following * characters later. */ return slcd_reget(state, pch, parg); } /* We expect the next character to be the second byte of hexidecimal * count value. */ if (!IS_HEX(ch)) { /* Not a 5-byte escape sequence. Return the ESC now; return the * following characters later. */ lcderr("ERROR: Parsing failed: ESC-L-%c followed by %02x\n", state->buf[NDX_COUNTH], ch); return slcd_reget(state, pch, parg); } /* Save the second character of the two byte hexidecimal number */ state->buf[NDX_COUNTL] = (uint8_t)ch; state->nch = NCH_COUNTL; /* Get the next character from the buffer */ ch = stream->get(stream); if (ch == EOF) { /* End of file/stream. Return the ESC now; return the following * characters later. */ return slcd_reget(state, pch, parg); } /* Put the character in the reget buffer because there is on more way * that we can fail. */ state->buf[NDX_CODE5] = (uint8_t)ch; state->nch = NCH_CODE5; /* Get the code and the count values. All count values must be greater * than 0 or something is wrong. */ code = CODE_RETURN(ch); count = slcd_nibble(state->buf[NDX_COUNTH]) << 4 | slcd_nibble(state->buf[NDX_COUNTL]); /* Verify the special CLCD action code */ if (code < (int)FIRST_SLCDCODE || code > (int)LAST_SLCDCODE) { /* Not a special command code. Return the ESC now and the rest * of the characters later. */ lcderr("ERROR: Parsing failed: ESC-L-%c-%c followed by %02x\n", state->buf[NDX_COUNTH], state->buf[NDX_COUNTL], ch); return slcd_reget(state, pch, parg); } } /* We have successfully parsed the entire escape sequence. Return the * CLCD value in pch, return the count in parg, and an indication that this * is a special action. */ *pch = code; *parg = count; state->nch = 0; return SLCDRET_SPEC; }