string_conversion_7bit_sms_unpacking()

uint8_t string_conversion_7bit_sms_unpacking	(	const uint8_t *	packed,
		uint8_t *	unpacked,
		uint8_t	num_char
	)

Performs unpacking of a packed GSM 7 bit string as described below.

   Packed data bits:
   bit number:   7   6   5   4   3   2   1   0
   data byte 0: 2g  1a  1b  1c  1d  1e  1f  1g      p0
   data byte 1: 3f  3g  2a  2b  2c  2d  2e  2f      p1
   data byte 2: 4e  4f  4g  3a  3b  3c  3d  3e      p2
   data byte 3: 5d  5e  5f  5g  4a  4b  4c  4d      p3
   data byte 4: 6c  6d  6e  6f  6g  5a  5b  5c      p4
   data byte 5: 7b  7c  7d  7e  7f  7g  6a  6b      p5
   data byte 6: 8a  8b  8c  8d  8e  8f  8g  7a      p6
   data byte 7: Ag  9a  9b  9c  9d  9e  9f  9g      p7
   data byte 8: Bf  Bg  Aa  Ab  Ac  Ad  Ae  Af      p8
   and so on...

   Unpacked data bits:
   bit number:   7   6   5   4   3   2   1   0
   data byte 0:  0  1a  1b  1c  1d  1e  1f  1g       p0 & 7F
   data byte 1:  0  2a  3b  2c  2d  2e  2f  2g      (p1 << 1 | p0 >> 7) & 7F
   data byte 2:  0  3a  3b  3c  3d  3e  3f  3g      (p2 << 2 | p1 >> 6) & 7F
   data byte 3:  0  4a  4b  4c  4d  4e  4f  4g      (p3 << 3 | p2 >> 5) & 7F
   data byte 4:  0  5a  5b  5c  5d  5e  5f  5g      (p4 << 4 | p3 >> 4) & 7F
   data byte 5:  0  6a  6b  6c  6d  6e  6f  6g      (p5 << 5 | p4 >> 3) & 7F
   data byte 6:  0  7a  7b  7c  7d  7e  7f  7g      (p6 << 6 | p5 >> 2) & 7F
   data byte 7:  0  8a  8b  8c  8d  8e  8f  8g      (p7 << 7 | p6 >> 1) & 7F
   data byte 8:  0  9a  9b  9c  9d  9e  9f  9g      (p7 << 0 | p6 >> 8) & 7F
   data byte 9:  0  Aa  Ab  Ac  Ad  Ae  Af  Ag      (p8 << 1 | p7 >> 7) & 7F
   data byte A:  0  Ba  Bb  Bc  Bd  Be  Bf  Bg      (p9 << 2 | p8 >> 6) & 7F
   and so on...

References: 3GPP TS 23.038 chapter 6.1.2.1: SMS Packing

Parameters

[in]	packed	Pointer to buffer containing the packed string.
[in]	num_char	Number of 7-bit characters (i.e. septets) to be unpacked, including possible escape codes. Also indicates maximum allowed number of characters to be stored to output buffer by this function.
[out]	unpacked	Pointer to buffer to store the unpacked string. Allocated size shall be at least "num_char" bytes.

Returns

Number of valid bytes/characters in the unpacked string "unpacked".