ro: implement NRO decompression and fix bugs

libraries/libstratosphere/source/util/util_compression_lz4.cpp

@@ -35,5 +35,151 @@ namespace ams::util {
         /* This is just a thin wrapper around LZ4. */
         return LZ4_decompress_safe(reinterpret_cast<const char *>(src), reinterpret_cast<char *>(dst), static_cast<int>(src_size), static_cast<int>(dst_size));
     }
-
+    
+    /* TODO: This was added for ro in 23.0.0+, but it's unclear if this is even part of the util namespace. */
+    /* It's similar to the official lz4frame code, but has additional constraints and uses static work buffers. */
+    /* Evaluate if we should use lz4frame instead and implement matching frame compression. */
+    int DecompressLZ4Frame(size_t* out_size, void *dst, size_t dst_size, const void *src, size_t src_size, void *src_work, size_t src_work_size, void *dst_work, size_t dst_work_size) {
+        /* Destination buffer must be behind source buffer. */
+        if (dst > src) {
+            std::memset(dst, 0, dst_size);
+            return -1;
+        }
+        
+        const char *src_end = static_cast<const char *>(src) + src_size;
+        const char *dst_end = static_cast<const char *>(dst) + dst_size;
+        
+        if ((src_end != dst_end) || (src_work_size != 0x10000) || (dst_work_size != 0x10000)) {
+            std::memset(dst, 0, dst_size);
+            return -1;
+        }
+        
+        if (src_size < 7) {
+            std::memset(dst, 0, dst_size);
+            return -2;
+        }
+        
+        const uint32_t magic = *reinterpret_cast<const uint32_t *>(src);
+        const uint8_t flg = *reinterpret_cast<const uint8_t *>(src) + 4;
+        const uint8_t bd = *reinterpret_cast<const uint8_t *>(src) + 5;
+        const uint8_t header_checksum = *reinterpret_cast<const uint8_t *>(src) + 6;
+        
+        /* Check for LZ4F_MAGICNUMBER, validate flags and block size. */
+        if ((magic != 0x184D2204) || ((flg & 1) != 0) || (flg != 0x60) || (bd != 0x40)) {
+            std::memset(dst, 0, dst_size);
+            return -2;
+        }
+        
+        /* TODO: Implement header checksum validation. This requires xxhash, do we want to have xxhash in util? */
+        AMS_UNUSED(header_checksum);
+        
+        uint32_t src_pos = 7; /* Skip the header. */
+        uint32_t dst_pos = 0;
+        
+        /* Destination size is too small. */
+        if (dst_size < src_pos) {
+            std::memset(dst, 0, dst_size);
+            return -2;
+        }
+        
+        while (true) {
+            /* Not enough space left. */
+            if ((dst_size - src_pos) < 4) {
+                std::memset(dst, 0, dst_size);
+                return -4;
+            }
+            
+            const char* src_data_block = reinterpret_cast<const char *>(src) + src_pos;
+            char* dst_data_block = reinterpret_cast<char *>(dst) + dst_pos;
+            
+            const uint32_t block_header = *reinterpret_cast<const uint32_t *>(src_data_block);
+            
+            /* We've reached the end. */
+            if (!block_header) {
+                break;
+            }
+            
+            const uint32_t block_size = block_header & 0x7FFFFFFF;
+            
+            /* Block size is invalid. */
+            if (block_size > 0x10000) {
+                std::memset(dst, 0, dst_size);
+                return -3;
+            }
+            
+            /* Advance the data block. */
+            src_data_block += sizeof(block_header);
+            
+            /* Block size is invalid. */
+            if ((dst_end - src_data_block) < block_size) {
+                std::memset(dst, 0, dst_size);
+                return -4;
+            }
+            
+            /* Copy the data block to the source work buffer. */
+            std::memcpy(static_cast<char *>(src_work), src_data_block, block_size);
+            
+            if ((block_header & 0x80000000) != 0) {
+                /* Block size is invalid. */
+                if ((dst_end - dst_data_block) < block_size) {
+                    std::memset(dst, 0, dst_size);
+                    return -4;
+                }
+                
+                dst_pos += block_size;
+                src_pos += block_size;
+                
+                /* Destination is overrunning source. */
+                if (dst_pos > src_pos) {
+                    std::memset(dst, 0, dst_size);
+                    return -5;
+                }
+                
+                /* This is a raw block, copy it. */
+                std::memmove(dst_data_block, src_data_block, block_size); 
+            } else {
+                /* This is a compressed block, decompress it. */
+                int decompressed_size = LZ4_decompress_safe(reinterpret_cast<const char *>(src_work), reinterpret_cast<char *>(dst_work), static_cast<int>(src_work_size), static_cast<int>(dst_work_size));
+                
+                /* Decompressed size is invalid. */
+                if (decompressed_size < 1) {
+                    std::memset(dst, 0, dst_size);
+                    return -3;
+                }
+                
+                /* Decompressed size is invalid. */
+                if ((dst_end - dst_data_block) < decompressed_size) {
+                    std::memset(dst, 0, dst_size);
+                    return -4;
+                }
+                
+                dst_pos += decompressed_size;
+                src_pos += block_size;
+                
+                /* Destination is overrunning source. */
+                if (dst_pos > src_pos) {
+                    std::memset(dst, 0, dst_size);
+                    return -5;
+                }
+                
+                /* Copy the decompressed data back. */
+                std::memcpy(dst_data_block, static_cast<char *>(dst_work), decompressed_size);
+            }
+            
+            /* We've exceeded the destination's size. */
+            if (src_pos >= dst_size) {
+                std::memset(dst, 0, dst_size);
+                return -2;
+            }   
+        }
+        
+        /* We didn't consume all data. */
+        if (src_pos != src_size) {
+            std::memset(dst, 0, dst_size);
+            return -2;
+        }
+        
+        *out_size = dst_pos;
+        return 0;
+    }
 }