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  • /*
     *  charset conversion utils
     *
     *  Copyright (c) 2017 Rob Clark
     *
     *  SPDX-License-Identifier:     GPL-2.0+
     */
    
    #include <charset.h>
    #include <malloc.h>
    
    /*
     * utf8/utf16 conversion mostly lifted from grub
     */
    
    size_t utf16_strlen(const uint16_t *in)
    {
    	size_t i;
    	for (i = 0; in[i]; i++);
    	return i;
    }
    
    size_t utf16_strnlen(const uint16_t *in, size_t count)
    {
    	size_t i;
    	for (i = 0; count-- && in[i]; i++);
    	return i;
    }
    
    uint16_t *utf16_strcpy(uint16_t *dest, const uint16_t *src)
    {
    	uint16_t *tmp = dest;
    
    	while ((*dest++ = *src++) != '\0')
    		/* nothing */;
    	return tmp;
    
    }
    
    uint16_t *utf16_strdup(const uint16_t *s)
    {
    	uint16_t *new;
    	if (!s || !(new = malloc((utf16_strlen(s) + 1) * 2)))
    		return NULL;
    	utf16_strcpy(new, s);
    	return new;
    }
    
    /* Convert UTF-16 to UTF-8.  */
    uint8_t *utf16_to_utf8(uint8_t *dest, const uint16_t *src, size_t size)
    {
    	uint32_t code_high = 0;
    
    	while (size--) {
    		uint32_t code = *src++;
    
    		if (code_high) {
    			if (code >= 0xDC00 && code <= 0xDFFF) {
    				/* Surrogate pair.  */
    				code = ((code_high - 0xD800) << 10) + (code - 0xDC00) + 0x10000;
    
    				*dest++ = (code >> 18) | 0xF0;
    				*dest++ = ((code >> 12) & 0x3F) | 0x80;
    				*dest++ = ((code >> 6) & 0x3F) | 0x80;
    				*dest++ = (code & 0x3F) | 0x80;
    			} else {
    				/* Error...  */
    				*dest++ = '?';
    				/* *src may be valid. Don't eat it.  */
    				src--;
    			}
    
    			code_high = 0;
    		} else {
    			if (code <= 0x007F) {
    				*dest++ = code;
    			} else if (code <= 0x07FF) {
    				*dest++ = (code >> 6) | 0xC0;
    				*dest++ = (code & 0x3F) | 0x80;
    			} else if (code >= 0xD800 && code <= 0xDBFF) {
    				code_high = code;
    				continue;
    			} else if (code >= 0xDC00 && code <= 0xDFFF) {
    				/* Error... */
    				*dest++ = '?';
    			} else if (code < 0x10000) {
    				*dest++ = (code >> 12) | 0xE0;
    				*dest++ = ((code >> 6) & 0x3F) | 0x80;
    				*dest++ = (code & 0x3F) | 0x80;
    			} else {
    				*dest++ = (code >> 18) | 0xF0;
    				*dest++ = ((code >> 12) & 0x3F) | 0x80;
    				*dest++ = ((code >> 6) & 0x3F) | 0x80;
    				*dest++ = (code & 0x3F) | 0x80;
    			}
    		}
    	}
    
    	return dest;
    }
    
    
    uint16_t *utf8_to_utf16(uint16_t *dest, const uint8_t *src, size_t size)
    {
    	while (size--) {
    		int extension_bytes;
    		uint32_t code;
    
    		extension_bytes = 0;
    		if (*src <= 0x7f) {
    			code = *src++;
    			/* Exit on zero byte */
    			if (!code)
    				size = 0;
    		} else if (*src <= 0xbf) {
    			/* Illegal code */
    			code = '?';
    		} else if (*src <= 0xdf) {
    			code = *src++ & 0x1f;
    			extension_bytes = 1;
    		} else if (*src <= 0xef) {
    			code = *src++ & 0x0f;
    			extension_bytes = 2;
    		} else if (*src <= 0xf7) {
    			code = *src++ & 0x07;
    			extension_bytes = 3;
    		} else {
    			/* Illegal code */
    			code = '?';
    		}
    
    		for (; extension_bytes && size; --size, --extension_bytes) {
    			if ((*src & 0xc0) == 0x80) {
    				code <<= 6;
    				code |= *src++ & 0x3f;
    			} else {
    				/* Illegal code */
    				code = '?';
    				++src;
    				--size;
    				break;
    			}
    		}
    
    		if (code < 0x10000) {
    			*dest++ = code;
    		} else {
    			/*
    			 * Simplified expression for
    			 * (((code - 0x10000) >> 10) & 0x3ff) | 0xd800
    			 */
    			*dest++ = (code >> 10) + 0xd7c0;
    			*dest++ = (code & 0x3ff) | 0xdc00;
    		}
    	}
    	return dest;
    }